WEBVTT 00:00:00.000 --> 00:00:02.620 Welcome to the Deep Dive, the only place where 00:00:02.620 --> 00:00:05.480 we take stacks of complicated research and distill 00:00:05.480 --> 00:00:08.560 it down to the essential, the surprising, and 00:00:08.560 --> 00:00:12.500 the truly mind -blowing. If you have ever bought 00:00:12.500 --> 00:00:16.179 a carton of milk, you know the name we are focusing 00:00:16.179 --> 00:00:19.420 on today, Louis Pasteur. And if that's all you 00:00:19.420 --> 00:00:22.500 know you are missing, I mean just the most incredible 00:00:22.500 --> 00:00:25.539 scientific journey of the 19th century, Pasteur 00:00:25.539 --> 00:00:28.620 wasn't just about food safety. He was a singular 00:00:28.620 --> 00:00:31.480 revolutionary who moved, you know, seamlessly 00:00:31.480 --> 00:00:33.719 from the abstract world of molecular chemistry 00:00:33.719 --> 00:00:36.719 to the practical life saving world of public 00:00:36.719 --> 00:00:38.820 health. He bridged fields that had just been 00:00:38.820 --> 00:00:41.320 operating in total isolation before him. And 00:00:41.320 --> 00:00:44.020 our mission today really is to unpack that for 00:00:44.020 --> 00:00:46.100 you. We're going to look at his career through 00:00:46.100 --> 00:00:49.219 four main pillars. For huge pillars as far as 00:00:49.219 --> 00:00:50.780 the chemistry. Right. This completely unexpected 00:00:50.780 --> 00:00:53.340 place. Right. Molecular chemistry. Then we move 00:00:53.340 --> 00:00:54.759 into the stuff people know a bit more about. 00:00:55.149 --> 00:00:58.210 Fermentation, germ theory. Pasteurization, of 00:00:58.210 --> 00:01:01.649 course. Of course. And then disease prevention. 00:01:01.770 --> 00:01:04.549 This is where it gets really intense. The silkworm 00:01:04.549 --> 00:01:08.079 crisis, his pioneering work in vaccination. And 00:01:08.079 --> 00:01:10.299 that's where it gets really dramatic. Yeah. And 00:01:10.299 --> 00:01:11.959 then finally, we have to talk about the controversy. 00:01:11.980 --> 00:01:15.480 We do. Because his legacy is not as simple as 00:01:15.480 --> 00:01:17.939 the milk carton makes it seem, especially with 00:01:17.939 --> 00:01:20.439 the revelation of his private notebooks. No, 00:01:20.480 --> 00:01:23.680 not at all. But it is a legacy that defines modern 00:01:23.680 --> 00:01:26.480 biology. When we talk about Pasteur, we're talking 00:01:26.480 --> 00:01:28.640 about a titan. One of the undisputed founders 00:01:28.640 --> 00:01:31.640 of modern bacteriology. Exactly. He's called 00:01:31.640 --> 00:01:34.379 the father of bacteriology. And he often shares 00:01:34.379 --> 00:01:36.900 the title father of microbiology with his great 00:01:36.900 --> 00:01:39.870 rival. Robert Cuff. And the work itself. I mean, 00:01:39.870 --> 00:01:42.769 the vaccines for anthrax and rabies alone are 00:01:42.769 --> 00:01:44.909 credited with saving millions of lives. They 00:01:44.909 --> 00:01:47.090 shifted global demographics. On a scale that 00:01:47.090 --> 00:01:49.530 was just unimaginable at the time. To really 00:01:49.530 --> 00:01:51.609 understand that scale, you have to appreciate 00:01:51.609 --> 00:01:54.370 the sheer distance he traveled. A career that 00:01:54.370 --> 00:01:56.329 starts with, what, looking at crystal shapes 00:01:56.329 --> 00:01:59.450 under a microscope and ends with injecting a 00:01:59.450 --> 00:02:02.329 virus into a child who was mauled by a rabid 00:02:02.329 --> 00:02:05.109 dog. It's an extraordinary trajectory. It really 00:02:05.109 --> 00:02:07.629 is. Okay. Let's unpack this journey, starting 00:02:07.629 --> 00:02:09.949 with the very surprising circumstances of his 00:02:09.949 --> 00:02:12.930 beginning. So Pasteur was born in Dulles, France 00:02:12.930 --> 00:02:19.069 in 1822. And his background was intensely humble. 00:02:19.289 --> 00:02:22.469 No silver spoon here. Not at all. His father 00:02:22.469 --> 00:02:25.810 was a poor tanner, Jean -Joseph Pasteur, who 00:02:25.810 --> 00:02:28.110 had been a sergeant in Napoleon's army. There 00:02:28.110 --> 00:02:30.530 was no inherited wealth, no academic family line 00:02:30.530 --> 00:02:32.569 to speak of. And when you look at the towering 00:02:32.569 --> 00:02:35.169 figure he became, it's genuinely startling to 00:02:35.169 --> 00:02:37.129 learn that his early academic career was just, 00:02:37.210 --> 00:02:40.449 well, it was marked by struggle and mediocrity. 00:02:40.490 --> 00:02:42.810 It was not some wunderkind who was destined for 00:02:42.810 --> 00:02:45.669 the laboratory. As a boy, his interests were 00:02:45.669 --> 00:02:48.270 mainly creative and outdoorsy. He loved to go 00:02:48.270 --> 00:02:50.550 fishing. And this is the surprising part. He 00:02:50.550 --> 00:02:52.449 was a really talented sketch artist. Really? 00:02:52.750 --> 00:02:54.810 Oh, yeah. We still have a collection of his early 00:02:54.810 --> 00:02:56.990 portraits and pastels of his family members. 00:02:57.439 --> 00:02:59.699 He seems to have had this, you know, meticulous 00:02:59.699 --> 00:03:01.960 attention to detail even back then, but he's 00:03:01.960 --> 00:03:04.580 applying it to art, not to equations. And academically, 00:03:04.680 --> 00:03:08.419 he hit a few roadblocks, right? He did. He failed 00:03:08.419 --> 00:03:11.479 his first examination for the École Normale Supérieure 00:03:11.479 --> 00:03:15.439 in 1841. He eventually got his Bachelor of Science 00:03:15.439 --> 00:03:19.240 in 1842. But even then, his grade in chemistry, 00:03:19.560 --> 00:03:22.340 the field where he would become a legend, was 00:03:22.340 --> 00:03:25.560 described as mediocre. Just mediocre. It's often 00:03:25.560 --> 00:03:27.759 suggested that he might have been dyslexic and 00:03:27.759 --> 00:03:30.360 dysgraphic based on his struggles with written 00:03:30.360 --> 00:03:32.219 language. It's a really interesting hypothesis 00:03:32.219 --> 00:03:34.560 that a man who struggled with a written word 00:03:34.560 --> 00:03:37.659 found his true voice in the physical world of 00:03:37.659 --> 00:03:40.159 experimentation and visualization. He just kept 00:03:40.159 --> 00:03:42.580 at it, though. He persisted. He finally entered 00:03:42.580 --> 00:03:45.400 the prestigious École Normale Supérieure in 1843 00:03:45.400 --> 00:03:48.439 after improving his standing. But his greatest 00:03:48.439 --> 00:03:50.300 intellectual breakthrough didn't happen in biology 00:03:50.300 --> 00:03:52.919 at all. It was in the highly abstract field of 00:03:52.919 --> 00:03:55.020 structural chemistry. And we're not just talking 00:03:55.020 --> 00:03:56.860 about a good paper. Some have described this 00:03:56.860 --> 00:03:59.960 as his most profound and most original contribution 00:03:59.960 --> 00:04:02.039 to science. That's it. This is the molecular 00:04:02.039 --> 00:04:05.780 breakthrough of 1848 dealing with tartrates and 00:04:05.780 --> 00:04:08.879 the concept of isomerism. That's right. And the 00:04:08.879 --> 00:04:11.360 problem had stumped chemists for decades. They 00:04:11.360 --> 00:04:13.159 were looking at two different forms of tartaric 00:04:13.159 --> 00:04:16.500 acid. Okay. One was derived naturally as a byproduct 00:04:16.500 --> 00:04:19.160 of winemaking. The other was synthesized in a 00:04:19.160 --> 00:04:22.339 lab. When they analyzed them chemically, they 00:04:22.339 --> 00:04:25.000 were identical. Same elements, same proportions. 00:04:25.339 --> 00:04:27.060 They should have been the same molecule. But 00:04:27.060 --> 00:04:29.060 they weren't. And the difference was only visible 00:04:29.060 --> 00:04:31.699 when you exposed them to polarized light. Exactly. 00:04:31.740 --> 00:04:34.160 Light, you know, it oscillates in all directions. 00:04:34.480 --> 00:04:36.639 When it's passed through a polarizing filter, 00:04:36.939 --> 00:04:39.620 the light waves are restricted to a single plane. 00:04:40.459 --> 00:04:43.339 The natural form of tartaric acid had this really 00:04:43.339 --> 00:04:47.720 curious property. When you dissolved it, it rotated 00:04:47.720 --> 00:04:50.500 that plane of polarized light to the right. This 00:04:50.500 --> 00:04:52.879 was called dextrorotatory. And the synthetic 00:04:52.879 --> 00:04:55.500 one? The chemically synthesized version did nothing. 00:04:55.600 --> 00:04:57.779 It was optically inactive. That's the puzzle, 00:04:57.839 --> 00:05:00.939 isn't it? Two compounds, same formula, but one 00:05:00.939 --> 00:05:03.060 twists light and the other doesn't. Why? I mean, 00:05:03.120 --> 00:05:06.019 scientists like Berzelius and Leibig were completely 00:05:06.019 --> 00:05:08.420 baffled. They were. They believed that if the 00:05:08.420 --> 00:05:10.680 composition was identical, the properties had 00:05:10.680 --> 00:05:12.699 to be identical. It was a fundamental assumption. 00:05:12.920 --> 00:05:15.439 And this is where Pasteur's background in crystallography 00:05:15.439 --> 00:05:18.189 becomes his superpower. It really does. He was 00:05:18.189 --> 00:05:20.670 studying the salts of racemic acid, that's the 00:05:20.670 --> 00:05:22.870 inactive synthetic form, and he observed that 00:05:22.870 --> 00:05:25.509 the mixture contained two distinct types of tiny 00:05:25.509 --> 00:05:27.850 crystals. Wait, so the synthetic mixture already 00:05:27.850 --> 00:05:30.689 had both forms in it. How did he even know to 00:05:30.689 --> 00:05:32.750 look for two separate crystal types if he didn't 00:05:32.750 --> 00:05:34.689 know about chirality yet? He was building on 00:05:34.689 --> 00:05:37.170 the work of the French mineralogist René Giustawi, 00:05:37.389 --> 00:05:39.889 who had shown that certain crystals that rotated 00:05:39.889 --> 00:05:43.290 light were asymmetrical. Pasteur noticed that 00:05:43.290 --> 00:05:45.870 the crystals in this racemic mixture, while identical 00:05:45.870 --> 00:05:49.790 in composition, were non -superimposable mirror 00:05:49.790 --> 00:05:52.250 images of each other. Like your left and right 00:05:52.250 --> 00:05:54.290 hand. A perfect analogy. They're reflections, 00:05:54.509 --> 00:05:56.829 but you cannot perfectly lay one on top of the 00:05:56.829 --> 00:05:58.509 other. They're different in a three -dimensional 00:05:58.509 --> 00:06:01.089 way. So he sees this, and then he has to act 00:06:01.089 --> 00:06:03.810 on it. He must have spent agonizing hours physically 00:06:03.810 --> 00:06:06.050 separating these microscopic crystals. It was 00:06:06.050 --> 00:06:08.800 an incredible, painstaking effort. He used only 00:06:08.800 --> 00:06:11.240 forceps and a microscope, sitting for hours, 00:06:11.379 --> 00:06:13.639 manually separating the right -handed crystals 00:06:13.639 --> 00:06:16.220 from the left -handed ones. It was purely based 00:06:16.220 --> 00:06:19.360 on their physical, visual asymmetry. And the 00:06:19.360 --> 00:06:21.920 result, once he put the separated piles into 00:06:21.920 --> 00:06:25.100 a solution, that must have been the true aha 00:06:25.100 --> 00:06:28.160 moment. You can just imagine it. When he dissolved 00:06:28.160 --> 00:06:30.300 the right -handed pile, it rotated polarized 00:06:30.300 --> 00:06:33.259 light to the right. Dextrorotatory. On a left 00:06:33.259 --> 00:06:35.980 -handed pile. Rotated light to the left. and 00:06:35.980 --> 00:06:38.680 when he mixed them back together in equal parts, 00:06:38.819 --> 00:06:40.279 just like they were in the original synthetic 00:06:40.279 --> 00:06:43.160 batch, the opposing rotations canceled each other 00:06:43.160 --> 00:06:45.839 out. Making the solution optically inactive. 00:06:46.019 --> 00:06:48.759 Mystery solved. Completely solved. So what does 00:06:48.759 --> 00:06:50.439 this all mean for the bigger picture? I mean, 00:06:50.459 --> 00:06:53.480 the significance here is enormous. It's massive. 00:06:54.120 --> 00:06:58.639 This experiment in 1848 was the very first demonstration 00:06:58.639 --> 00:07:02.220 of molecular chirality. The idea that molecules 00:07:02.220 --> 00:07:04.879 can exist as these non -superimposable mirror 00:07:04.879 --> 00:07:07.779 images, we call them enantiomers now. It was 00:07:07.779 --> 00:07:10.759 the first real explanation of isomerism beyond 00:07:10.759 --> 00:07:13.800 just basic composition. It basically forced chemists 00:07:13.800 --> 00:07:16.439 to start thinking in three dimensions. And the 00:07:16.439 --> 00:07:18.339 impact on structural chemistry was immediate. 00:07:18.420 --> 00:07:20.040 But think about the impact on medicine today. 00:07:20.300 --> 00:07:23.519 A drug's efficacy often depends entirely on whether 00:07:23.519 --> 00:07:25.740 it's the right or left -handed version of a molecule. 00:07:26.250 --> 00:07:28.490 Right. Sometimes one version works and the mirror 00:07:28.490 --> 00:07:32.009 image is inert or even toxic. Exactly. And Pasteur, 00:07:32.050 --> 00:07:35.750 this poor Tanner's son, laid the absolute bedrock 00:07:35.750 --> 00:07:38.550 for that entire field of understanding. He even 00:07:38.550 --> 00:07:40.970 showed that life itself, specifically the mold 00:07:40.970 --> 00:07:43.649 used in fermentation, had a preference for one 00:07:43.649 --> 00:07:47.610 form. The natural dextrorotatory one. Yes. Life 00:07:47.610 --> 00:07:50.240 is chiral. And that observation, that connection 00:07:50.240 --> 00:07:52.560 between the abstract world of crystals and the 00:07:52.560 --> 00:07:55.220 living world of biology, is the exact transition 00:07:55.220 --> 00:07:57.579 that defines the next stage of his career. So 00:07:57.579 --> 00:07:59.920 Pasteur's shift from crystallography to biology 00:07:59.920 --> 00:08:03.199 wasn't just, you know, abstract curiosity. It 00:08:03.199 --> 00:08:05.399 was intensely practical. Oh, and economically 00:08:05.399 --> 00:08:08.259 vital. In 1856, he was dean at the University 00:08:08.259 --> 00:08:10.600 of Lille, which is a big industrial city heavily 00:08:10.600 --> 00:08:13.319 involved in alcohol production. And a local wine 00:08:13.319 --> 00:08:16.240 manufacturer, a man named M. Bijot, came to him 00:08:16.240 --> 00:08:18.980 with an industrial crisis. A huge crisis. His 00:08:18.980 --> 00:08:21.699 beetroot alcohol kept souring, and his wine was 00:08:21.699 --> 00:08:23.899 spoiling way too easily. He was losing money 00:08:23.899 --> 00:08:26.600 hand over fist. So a pastor takes this problem 00:08:26.600 --> 00:08:28.860 from a beer vet and essentially turns it into 00:08:28.860 --> 00:08:32.360 the germ theory of disease. But he starts by 00:08:32.360 --> 00:08:34.419 tackling the prevailing theory of fermentation, 00:08:34.639 --> 00:08:37.360 which was basically chemical dogma at the time. 00:08:37.539 --> 00:08:40.240 It was scientific gospel, championed by huge 00:08:40.240 --> 00:08:43.629 names like Liebig and... Berzelius. Their theory 00:08:43.629 --> 00:08:45.769 was that fermentation sugar turning into alcohol 00:08:45.769 --> 00:08:49.090 was a purely non -living chemical process. A 00:08:49.090 --> 00:08:52.049 process of decomposition. Exactly, or putrefaction. 00:08:52.169 --> 00:08:54.470 They saw the yeast as just a protein compound 00:08:54.470 --> 00:08:56.789 in the process of decaying, and they thought 00:08:56.789 --> 00:08:58.950 that decay somehow kicked off the decomposition 00:08:58.950 --> 00:09:01.350 of the sugar. And Pasteur showed this theory 00:09:01.350 --> 00:09:03.529 was completely backward. How did he prove it 00:09:03.529 --> 00:09:06.149 was life, not decay, that was responsible? He 00:09:06.149 --> 00:09:08.490 used his microscope. the same one he used for 00:09:08.490 --> 00:09:10.769 looking at those crystal facets he looked at 00:09:10.769 --> 00:09:13.210 the fermenting liquid and realized that the yeast 00:09:13.210 --> 00:09:15.850 which everyone thought was just a chemical precipitate 00:09:15.850 --> 00:09:18.529 was actually a living organism it was alive it 00:09:18.529 --> 00:09:21.470 was alive and through these meticulous experiments 00:09:21.470 --> 00:09:24.289 like cultivating yeast in media that was free 00:09:24.289 --> 00:09:27.350 from any external contamination he proved that 00:09:27.350 --> 00:09:29.610 living yeast was solely and directly responsible 00:09:29.610 --> 00:09:33.100 for converting sugar into alcohol Fermentation 00:09:33.100 --> 00:09:36.720 was a biological process, a life process. Not 00:09:36.720 --> 00:09:39.039 just a simple chemical breakdown. Not at all. 00:09:39.139 --> 00:09:41.200 And this is where he makes the leap from how 00:09:41.200 --> 00:09:44.220 alcohol is made to how things spoil. He extends 00:09:44.220 --> 00:09:46.840 that finding to the sour wine problem. Exactly. 00:09:47.120 --> 00:09:49.120 When the wine went sour, he looked under the 00:09:49.120 --> 00:09:51.500 microscope again. And he found that when a different 00:09:51.500 --> 00:09:54.320 microorganism, usually a little rod -shaped bacterium 00:09:54.320 --> 00:09:56.379 instead of the spherical yeast, contaminated 00:09:56.379 --> 00:09:58.480 the wine. The fermentation went wrong. It went 00:09:58.480 --> 00:10:00.379 completely awry. Instead of producing ethanol, 00:10:00.639 --> 00:10:03.230 this contaminated... microorganism produced lactic 00:10:03.230 --> 00:10:05.509 acid, and that's what made the wine sour and 00:10:05.509 --> 00:10:07.950 undrinkable. This was the direct, undeniable 00:10:07.950 --> 00:10:11.789 link. Microbial growth causes product spoilage. 00:10:11.970 --> 00:10:14.149 It sounds so simple to us today, but in the mid 00:10:14.149 --> 00:10:16.490 -19th century, this was radical. It was moving 00:10:16.490 --> 00:10:18.649 the entire scientific world away from these vague 00:10:18.649 --> 00:10:22.529 ideas of bad air or spontaneous detail and into 00:10:22.529 --> 00:10:25.029 the measurable world of living microbes. And 00:10:25.029 --> 00:10:26.909 what's also fascinating is the nuance he found. 00:10:27.279 --> 00:10:29.759 This research led to a major side observation 00:10:29.759 --> 00:10:32.759 in 1861, which we now call the Pasteur effect. 00:10:33.080 --> 00:10:35.679 Okay, what's that? He noticed that yeast fermented 00:10:35.679 --> 00:10:38.659 sugar at a significantly lower rate when it was 00:10:38.659 --> 00:10:42.139 exposed to air aerobically compared to when oxygen 00:10:42.139 --> 00:10:45.720 was absent. So oxygen was actually slowing the 00:10:45.720 --> 00:10:48.620 fermentation down? Yes. He figured out that when 00:10:48.620 --> 00:10:51.200 oxygen was present, the yeast could respire more 00:10:51.200 --> 00:10:53.879 efficiently. It needed less sugar for energy, 00:10:54.019 --> 00:10:56.700 so it used more for growth rather than for fermentation. 00:10:56.779 --> 00:10:59.320 But when you took the oxygen away... It had to 00:10:59.320 --> 00:11:01.980 switch to the much less efficient anaerobic process 00:11:01.980 --> 00:11:04.620 of fermentation just to survive, and so it had 00:11:04.620 --> 00:11:08.159 to chew through sugar much, much faster. It was 00:11:08.159 --> 00:11:10.419 this beautiful illustration of microbial metabolism. 00:11:10.860 --> 00:11:13.279 And it completely demolished the old decomposition 00:11:13.279 --> 00:11:16.179 theory. It did. And all of this work led to his 00:11:16.179 --> 00:11:19.960 most recognizable invention. If invisible microorganisms 00:11:19.960 --> 00:11:22.679 cause spoilage, then the solution is to kill 00:11:22.679 --> 00:11:25.279 them. This is the birth of pasteurization. A 00:11:25.279 --> 00:11:28.539 simple, elegant industrial solution. Exactly. 00:11:29.000 --> 00:11:30.960 For the wine and beer makers who were losing 00:11:30.960 --> 00:11:33.700 fortunes, Pasteur recommended just heating the 00:11:33.700 --> 00:11:37.509 liquids. Pasteurization, named after him, involves 00:11:37.509 --> 00:11:39.549 heating a liquid to a controlled temperature, 00:11:39.789 --> 00:11:43.370 say between 60 and 100 degrees Celsius, for a 00:11:43.370 --> 00:11:45.929 specific time. And that heat is enough to kill 00:11:45.929 --> 00:11:48.470 most of the bacteria and molds, the contaminating 00:11:48.470 --> 00:11:50.690 agents, without ruining the product's flavor. 00:11:50.909 --> 00:11:53.049 Right. He and Claude Bernard completed testing 00:11:53.049 --> 00:11:55.629 even on things like blood and urine samples in 00:11:55.629 --> 00:11:58.929 1862, and the process was patented for wine in 00:11:58.929 --> 00:12:02.169 1865. The economic relief for the French wine 00:12:02.169 --> 00:12:05.149 industry was immediate and massive. But the truly 00:12:05.149 --> 00:12:07.590 colossal leave wasn't saving wine. It was the 00:12:07.590 --> 00:12:10.850 application to medicine. That's the real breakthrough. 00:12:11.070 --> 00:12:14.190 If microorganisms could ruin beer and sour wine, 00:12:14.429 --> 00:12:16.809 what happens if those same microorganisms get 00:12:16.809 --> 00:12:19.649 into an animal or a human? That was the revolutionary 00:12:19.649 --> 00:12:22.710 idea. The idea that invisible germs cause disease. 00:12:22.850 --> 00:12:25.509 The germ theory had been proposed before, but 00:12:25.509 --> 00:12:27.970 Pasteur provided the irrefutable evidence straight 00:12:27.970 --> 00:12:30.230 from the laboratory and the industrial vat. And 00:12:30.230 --> 00:12:32.620 the ripple effect was instant. This connection 00:12:32.620 --> 00:12:35.559 profoundly influenced Joseph Lister, the British 00:12:35.559 --> 00:12:37.980 surgeon. Lister immediately applied the principle 00:12:37.980 --> 00:12:41.379 to his work. If germs cause spoilage, they must 00:12:41.379 --> 00:12:45.000 cause surgical sepsis. So Lister developed antiseptic 00:12:45.000 --> 00:12:48.139 surgical methods using carbolic acid to prevent 00:12:48.139 --> 00:12:50.360 those invisible organisms from getting into the 00:12:50.360 --> 00:12:53.690 patient's body during an operation. And it revolutionized 00:12:53.690 --> 00:12:56.429 surgery. It dramatically reduced mortality rates 00:12:56.429 --> 00:12:59.690 from infection. It did. So we've moved from tartaric 00:12:59.690 --> 00:13:02.970 acid crystals to antiseptic surgery in just over 00:13:02.970 --> 00:13:05.730 a decade. But the next stage of his career involves 00:13:05.730 --> 00:13:08.470 tackling really the philosophical fight of the 00:13:08.470 --> 00:13:10.769 age. That's a great way to put it. The work on 00:13:10.769 --> 00:13:13.330 fermentation was about life causing change. The 00:13:13.330 --> 00:13:15.710 next big battle was about how life starts. And 00:13:15.710 --> 00:13:18.250 this was one of the most contentious, high stakes 00:13:18.250 --> 00:13:21.419 debates of the 19th century. spontaneous generation. 00:13:21.779 --> 00:13:23.899 For our listeners, spontaneous generation was 00:13:23.899 --> 00:13:26.159 this ancient doctrine going all the way back 00:13:26.159 --> 00:13:28.419 to Aristotle. The idea that living organisms 00:13:28.419 --> 00:13:31.519 could just arise, you know, spontaneously from 00:13:31.519 --> 00:13:33.820 nonliving matter. Maggots from spoiled meat, 00:13:33.899 --> 00:13:37.460 mice from old rags. Right. Or in the 19th century 00:13:37.460 --> 00:13:40.379 context, life just springing forth from a sterilized 00:13:40.379 --> 00:13:43.240 liquid simply by being exposed to air. And this 00:13:43.240 --> 00:13:46.000 idea was fiercely championed by figures like 00:13:46.000 --> 00:13:48.610 Felix Archimede Pouchet. Pouchet was the director 00:13:48.610 --> 00:13:50.950 of the Rouen Museum of Natural History, and he 00:13:50.950 --> 00:13:55.230 argued forcefully that air, even cure air, possessed 00:13:55.230 --> 00:13:58.289 some kind of creative, vital force that could 00:13:58.289 --> 00:14:00.870 spontaneously generate life. This wasn't just 00:14:00.870 --> 00:14:03.669 a quiet academic argument. The implications were 00:14:03.669 --> 00:14:06.509 enormous, touching on the origins of life itself. 00:14:06.830 --> 00:14:09.210 So big that the French Academy of Sciences wanted 00:14:09.210 --> 00:14:12.399 it settled. In 1860, they offered the Alhambra 00:14:12.399 --> 00:14:16.379 Prize as substantial 2 ,500 francs to whoever 00:14:16.379 --> 00:14:19.200 could definitively prove or disprove the doctrine. 00:14:19.399 --> 00:14:21.679 And Pasteur went right after that prize. He did, 00:14:21.840 --> 00:14:24.379 and he won it in 1862 through a series of experiments 00:14:24.379 --> 00:14:27.039 that are just legendary for their clarity and 00:14:27.039 --> 00:14:29.539 elegance. His approach wasn't to argue philosophy. 00:14:29.759 --> 00:14:32.279 It was to use the microscope and controlled contamination 00:14:32.279 --> 00:14:35.019 to prove where this spontaneous life was actually 00:14:35.019 --> 00:14:37.179 coming from. And it was coming from the environment. 00:14:37.460 --> 00:14:40.200 Exactly. He first replicated the classic experiments. 00:14:40.419 --> 00:14:42.779 He showed that if you sterilized a liquid broth 00:14:42.779 --> 00:14:45.240 by boiling it and then sealed the container completely, 00:14:45.600 --> 00:14:48.159 nothing grew. Okay, so that suggests that something 00:14:48.159 --> 00:14:50.759 from the outside, presumably the air, was necessary. 00:14:51.139 --> 00:14:53.840 But how do you prove it's dust in the air and 00:14:53.840 --> 00:14:56.500 not the air itself? He had a stroke of genius 00:14:56.500 --> 00:14:59.460 with his altitude tests. He took a series of 00:14:59.460 --> 00:15:02.440 flasks with boiled, sterilized broths and carried 00:15:02.440 --> 00:15:04.659 them to different altitudes. He went up to the 00:15:04.659 --> 00:15:07.019 high purity of the Mer de Glace glacier in the 00:15:07.019 --> 00:15:09.539 Alps, but he also did tests in the contaminated 00:15:09.539 --> 00:15:12.279 air of Paris. And the method was just to open 00:15:12.279 --> 00:15:14.440 the flasks for a moment, expose them to the air, 00:15:14.480 --> 00:15:16.960 and then seal them back up. Precisely. And he 00:15:16.960 --> 00:15:19.000 would count how many flasks subsequently showed 00:15:19.000 --> 00:15:22.159 microbial growth. Down in the polluted air of 00:15:22.159 --> 00:15:24.639 the Paris streets, nearly all the flasks quickly 00:15:24.639 --> 00:15:27.059 showed growth. But up on the mountain? High up 00:15:27.059 --> 00:15:29.500 on the glacier, where the air was demonstrably 00:15:29.500 --> 00:15:32.460 cleaner and had less dust, very, very few of 00:15:32.460 --> 00:15:34.659 them showed any growth at all. That's a powerful 00:15:34.659 --> 00:15:36.960 distinction. It proved the germs were airborne, 00:15:37.179 --> 00:15:39.620 attached to dust particles, not some mysterious 00:15:39.620 --> 00:15:42.600 property of pure air. Right. The presence of 00:15:42.600 --> 00:15:45.259 the dust determined the outcome. And then we 00:15:45.259 --> 00:15:46.860 come to the experiment that sealed the deal. 00:15:47.220 --> 00:15:51.159 The one everyone recognizes. The swan neck flasks. 00:15:51.200 --> 00:15:54.000 The iconic experiment. It is truly the perfect 00:15:54.000 --> 00:15:57.419 definitive experiment. It illustrates the principle 00:15:57.419 --> 00:16:00.820 with flawless clarity. So describe the setup 00:16:00.820 --> 00:16:03.720 for our listeners. What was the key feature of 00:16:03.720 --> 00:16:06.820 this design? The flasks were specially designed 00:16:06.820 --> 00:16:09.720 with these long curving necks shaped like an 00:16:09.720 --> 00:16:13.019 S or a swan's neck. Pastor, you boiled the nutrient 00:16:13.019 --> 00:16:16.120 broth inside to sterilize it. The key was that 00:16:16.120 --> 00:16:19.279 the neck was open to the atmosphere. Air. the 00:16:19.279 --> 00:16:22.159 supposed source of spontaneous life, could freely 00:16:22.159 --> 00:16:24.799 get in. But the crucial element was gravity. 00:16:25.039 --> 00:16:28.379 Yes. As air currents moved in and out, the heavier 00:16:28.379 --> 00:16:30.559 dust particles, which had the actual germs on 00:16:30.559 --> 00:16:33.039 them, were trapped by gravity and moisture in 00:16:33.039 --> 00:16:34.759 the curves of the neck. So they could never reach 00:16:34.759 --> 00:16:37.419 the broth. Never. And for months, even years, 00:16:37.559 --> 00:16:40.000 the broth remained perfectly sterile. It proved 00:16:40.000 --> 00:16:42.340 that life doesn't just arise spontaneously. You 00:16:42.340 --> 00:16:44.519 could have pure air circulating. But without 00:16:44.519 --> 00:16:46.639 the dust, the contamination never happens. And 00:16:46.639 --> 00:16:48.539 the only way to contaminate it was to do what 00:16:48.539 --> 00:16:50.740 Pasteur dramatically demonstrated. You'd tilt 00:16:50.740 --> 00:16:52.720 the flask, let the sterile liquid flow down, 00:16:52.759 --> 00:16:54.820 and touch the accumulated dust in the neck, and 00:16:54.820 --> 00:16:56.899 then tilt it back. And then microbial growth 00:16:56.899 --> 00:16:59.460 would begin almost immediately. Instantly, it 00:16:59.460 --> 00:17:02.340 was the definitive refutation of a doctrine that 00:17:02.340 --> 00:17:05.079 had stood for millennia. He was absolutely justified 00:17:05.079 --> 00:17:08.119 in his dramatic conclusion. Never will the doctrine 00:17:08.119 --> 00:17:10.660 of spontaneous generation recover from the mortal 00:17:10.660 --> 00:17:13.579 blow of this simple experiment. The concept of 00:17:13.579 --> 00:17:16.920 biogenesis, that life only comes from life, was 00:17:16.920 --> 00:17:19.720 established and the germ theory of disease gained 00:17:19.720 --> 00:17:22.420 enormous, enormous credence. And that focus on 00:17:22.420 --> 00:17:25.180 contamination and life from life leads us directly 00:17:25.180 --> 00:17:28.200 to the next phase, tackling a devastating biological 00:17:28.200 --> 00:17:31.609 crisis that threatened an entire industry. The 00:17:31.609 --> 00:17:34.230 silkworm crisis is such a crucial part of Pasteur's 00:17:34.230 --> 00:17:36.450 story because it shows him applying abstract 00:17:36.450 --> 00:17:40.049 microbiology to this massive, messy, real -world 00:17:40.049 --> 00:17:43.369 economic disaster. Right. By 1865, two devastating 00:17:43.369 --> 00:17:45.650 diseases were just decimating silkworm farms 00:17:45.650 --> 00:17:48.150 across France and Europe. The national silk industry 00:17:48.150 --> 00:17:50.390 was on the brink of collapse. This was a political 00:17:50.390 --> 00:17:52.950 issue as much as a scientific one. A powerful 00:17:52.950 --> 00:17:56.029 chemist and senator, Jean -Baptiste Dumas, personally 00:17:56.029 --> 00:17:58.369 called on Pasteur to intervene. This wasn't a 00:17:58.369 --> 00:18:00.329 lab experiment anymore. This was a national emergency. 00:18:00.779 --> 00:18:04.220 So Pasteur spent five intensive years, from 1865 00:18:04.220 --> 00:18:08.299 to 1870, mostly in Alès, studying this problem. 00:18:08.599 --> 00:18:10.960 And he had to deal with two distinct diseases. 00:18:11.420 --> 00:18:13.640 That's right. First, there was pebrine, which 00:18:13.640 --> 00:18:15.900 was characterized by these cornelia corpuscles 00:18:15.900 --> 00:18:19.000 and black spots on the worms. And second, flashery, 00:18:19.000 --> 00:18:21.279 or dead flat disease, where the worms just became 00:18:21.279 --> 00:18:24.839 soft and flaccid and died quickly. And this chapter 00:18:24.839 --> 00:18:26.920 is so important because unlike the fermentation 00:18:26.920 --> 00:18:29.240 experiments or the spontaneous generation debate, 00:18:29.599 --> 00:18:32.400 Pasteur wasn't instantly the genius here. He 00:18:32.400 --> 00:18:35.079 made significant documented errors at the start. 00:18:35.259 --> 00:18:37.839 That's vital to acknowledge. His first major 00:18:37.839 --> 00:18:40.720 stumble was scientific simplification. He initially 00:18:40.720 --> 00:18:42.799 believed that Pebrine and Flashery were either 00:18:42.799 --> 00:18:44.720 the same disease or at least closely related. 00:18:44.920 --> 00:18:47.220 He was treating them as one single pathological 00:18:47.220 --> 00:18:49.500 process. How long did that last? It took him 00:18:49.500 --> 00:18:52.480 two years, until 1867, to clearly distinguish 00:18:52.480 --> 00:18:54.500 between the two separate conditions, each with 00:18:54.500 --> 00:18:56.920 its own cause and its own mode of transmission. 00:18:57.220 --> 00:18:59.859 And his second mistake was about the cause of 00:18:59.859 --> 00:19:02.759 Pebrine. Other researchers, particularly Antoine 00:19:02.759 --> 00:19:04.980 Béchamp, who we'll talk about later, had already 00:19:04.980 --> 00:19:07.839 suggested the disease was parasitic or microbial. 00:19:08.200 --> 00:19:10.900 focusing on those corpuscles. Right. But Pasteur 00:19:10.900 --> 00:19:13.779 initially rejected that. He saw the corpuscles 00:19:13.779 --> 00:19:16.240 as just a symptom of degeneration, not the active 00:19:16.240 --> 00:19:18.079 cause of the illness. But he did change his mind. 00:19:18.220 --> 00:19:21.759 He changed his mind by 1867. He finally conceded 00:19:21.759 --> 00:19:24.359 that the corpuscles, which we now know are spores 00:19:24.359 --> 00:19:27.200 of a microsporidian parasite, were indeed the 00:19:27.200 --> 00:19:30.240 causative agent of pabrine. For Flachery, he 00:19:30.240 --> 00:19:32.920 correctly identified a bacterial component, even 00:19:32.920 --> 00:19:34.839 though we now think the primary cause is viral. 00:19:35.289 --> 00:19:37.769 But for the time, attributing both to microbes 00:19:37.769 --> 00:19:40.509 was a major step. A huge step. And despite the 00:19:40.509 --> 00:19:43.190 initial missteps, he developed a profoundly effective 00:19:43.190 --> 00:19:46.269 solution for pabrine that basically saved the 00:19:46.269 --> 00:19:48.650 industry. What was the method? It was a simple 00:19:48.650 --> 00:19:51.509 yet rigorous quality control measure based entirely 00:19:51.509 --> 00:19:55.009 on his microscopy skills. He mandated this stringent 00:19:55.009 --> 00:19:57.470 sorting process, focusing on the mother moth, 00:19:57.470 --> 00:20:00.089 the female that laid the eggs, or the seed. So 00:20:00.089 --> 00:20:02.529 once the moth laid her eggs, what happened? The 00:20:02.529 --> 00:20:05.049 moth was immediately crushed into a pulp and 00:20:05.049 --> 00:20:07.390 examined under the mitroscope. Oh, wow. Yeah. 00:20:07.670 --> 00:20:10.190 If the characteristic pabrain corpuscles were 00:20:10.190 --> 00:20:12.769 found in the mother's tissues, the entire batch 00:20:12.769 --> 00:20:16.170 of eggs laid by that moth was immediately destroyed. 00:20:16.779 --> 00:20:19.559 not used for breeding. But if the mother was 00:20:19.559 --> 00:20:22.460 clean, the eggs were deemed healthy seed and 00:20:22.460 --> 00:20:24.539 allowed to proceed. So this just stopped the 00:20:24.539 --> 00:20:26.940 hereditary transmission of the disease in its 00:20:26.940 --> 00:20:30.059 tracks. Precisely. It broke the cycle of infection 00:20:30.059 --> 00:20:32.319 being passed from one generation of moths to 00:20:32.319 --> 00:20:35.440 the next. This simple, systematic sorting method 00:20:35.440 --> 00:20:38.240 dramatically reduced the incidence of pay brine 00:20:38.240 --> 00:20:40.740 and rescued the silk industry. And for flashery. 00:20:41.069 --> 00:20:44.049 Prevention there relied more on hygiene, making 00:20:44.049 --> 00:20:46.490 sure the moths were clean and the silkworms weren't 00:20:46.490 --> 00:20:49.210 eating contaminated food. It was a massive victory 00:20:49.210 --> 00:20:52.069 for applied microbiology and disease control, 00:20:52.190 --> 00:20:54.670 and it cemented his reputation as a national 00:20:54.670 --> 00:20:57.529 problem solver. The silkworm work really solidified 00:20:57.529 --> 00:20:59.849 his germ theory credentials. But the next phase, 00:21:00.069 --> 00:21:02.509 this is what cemented his position as one of 00:21:02.509 --> 00:21:04.630 the great medical innovators, the development 00:21:04.630 --> 00:21:07.319 of artificial vaccination. We know the concept 00:21:07.319 --> 00:21:10.119 of using a weak disease to confer immunity was 00:21:10.119 --> 00:21:12.819 already established, right? Edward Jenner's work 00:21:12.819 --> 00:21:15.640 with cowpox and smallpox almost a century earlier. 00:21:15.859 --> 00:21:18.779 Right. Jenner used a naturally occurring, related, 00:21:18.960 --> 00:21:23.220 but weaker disease cowpox, or vaccinia. Pasteur's 00:21:23.220 --> 00:21:25.160 revolutionary contribution was proving that you 00:21:25.160 --> 00:21:27.279 didn't need a natural variant. You could take 00:21:27.279 --> 00:21:30.079 a deadly pathogen and artificially weaken it. 00:21:30.430 --> 00:21:33.569 or attenuate it in the laboratory to create that 00:21:33.569 --> 00:21:36.490 safe immunity. And he honored Jenner by applying 00:21:36.490 --> 00:21:39.029 the term vaccines to these artificially weakened 00:21:39.029 --> 00:21:42.410 pathogens. He did. His first successful, though 00:21:42.410 --> 00:21:45.369 imperfect, attempt at this involved chicken cholera. 00:21:45.660 --> 00:21:48.339 which is caused by the bacterium Pastorella multicida. 00:21:48.500 --> 00:21:51.220 Ah, the famous story of the serendipitous discovery. 00:21:51.599 --> 00:21:53.440 One of the great tales of scientific chance. 00:21:53.759 --> 00:21:57.240 In 1879, Pasteur's assistants, Emile Roux and 00:21:57.240 --> 00:21:59.519 Charles Chamberlain, were growing cultures of 00:21:59.519 --> 00:22:01.519 the chicken cholera bacteria. They went away 00:22:01.519 --> 00:22:03.380 for a summer break. And they left a culture sitting 00:22:03.380 --> 00:22:05.200 out. They left a culture sitting out, exposed 00:22:05.200 --> 00:22:07.660 to air, for months. It had been sitting since 00:22:07.660 --> 00:22:10.420 July, and it lost its virulence. So when they 00:22:10.420 --> 00:22:13.619 came back and used this old, weakened culture, 00:22:14.519 --> 00:22:17.539 What happened to the chickens? The chickens they 00:22:17.539 --> 00:22:19.579 inoculated with the old culture got a little 00:22:19.579 --> 00:22:21.619 sick, but they didn't die. They recovered completely. 00:22:21.940 --> 00:22:24.299 Then the assistants tried to kill these same 00:22:24.299 --> 00:22:27.319 chickens with a fresh, virulent culture, which 00:22:27.319 --> 00:22:29.720 should have been lethal. But the chickens were 00:22:29.720 --> 00:22:33.539 immune. The prolonged exposure to air had attenuated 00:22:33.539 --> 00:22:36.119 the pathogen without killing it, creating a protective 00:22:36.119 --> 00:22:38.859 memory in the chicken's immune system. That initial 00:22:38.859 --> 00:22:42.059 observation that the old culture lost its virulence, 00:22:42.160 --> 00:22:44.799 that was the key insight? But it wasn't a completely 00:22:44.799 --> 00:22:48.079 smooth process, was it? No, not at all. While 00:22:48.079 --> 00:22:49.980 the general principle of attenuation was sound, 00:22:50.240 --> 00:22:52.779 getting the chicken cholera vaccine to work reliably 00:22:52.779 --> 00:22:56.099 was difficult. Pasteur attributed the attenuation 00:22:56.099 --> 00:22:58.819 to oxygen, thinking it interfered with the bacterial 00:22:58.819 --> 00:23:01.160 metabolism. But the vaccine itself was later 00:23:01.160 --> 00:23:03.420 found to be kind of inconsistent? Yeah, it was 00:23:03.420 --> 00:23:06.339 later proven ineffective by others. But it provided 00:23:06.339 --> 00:23:09.359 the essential conceptual roadmap. Pathogens can 00:23:09.359 --> 00:23:11.240 be artificially weakened by controlling their 00:23:11.240 --> 00:23:14.380 environment. And that roadmap led directly to 00:23:14.380 --> 00:23:16.819 a much greater challenge and a much greater triumph. 00:23:17.339 --> 00:23:20.759 Anthrax. Anthrax, caused by Bacillus anthracis. 00:23:20.960 --> 00:23:23.839 It was an economic killer, especially for cattle 00:23:23.839 --> 00:23:27.000 and sheep, creating those grimly named cursed 00:23:27.000 --> 00:23:30.140 fields across Europe. Pasteur's first contribution 00:23:30.140 --> 00:23:33.259 was environmental. He figured out that earthworms 00:23:33.259 --> 00:23:35.380 were bringing the resilient anthrax spores up 00:23:35.380 --> 00:23:37.779 to the surface from the buried bodies of infected 00:23:37.779 --> 00:23:40.579 animals. Right. He told farmers to stop burying 00:23:40.579 --> 00:23:43.180 dead stock in their fields. But developing the 00:23:43.180 --> 00:23:45.819 vaccine was complex because the anthrax bacillus 00:23:45.819 --> 00:23:48.759 was different from chicken cholera. It formed 00:23:48.759 --> 00:23:51.460 these extremely hardy spores. So just exposing 00:23:51.460 --> 00:23:53.500 them to air wouldn't work. Wouldn't touch them. 00:23:53.619 --> 00:23:56.319 Oh. The spores are highly resistant. So his lab 00:23:56.319 --> 00:23:58.579 had to find another controlled variable. They 00:23:58.579 --> 00:24:00.519 eventually discovered that by growing the anthrax 00:24:00.519 --> 00:24:03.000 bacilli at a slightly elevated temperature, specifically 00:24:03.000 --> 00:24:06.059 42 degrees Celsius, they could stop them from 00:24:06.059 --> 00:24:08.559 producing spores. So that weakened them. Exactly. 00:24:08.599 --> 00:24:11.339 The bacteria survived, but their virulence was 00:24:11.339 --> 00:24:13.859 significantly reduced, creating a safe, live, 00:24:14.039 --> 00:24:16.960 attenuated vaccine. Which brings us to the ultimate 00:24:16.960 --> 00:24:20.140 PR and scientific triumph, the Pouilly -Lafour 00:24:20.140 --> 00:24:24.119 experiment in 1881. This was a massive public 00:24:24.119 --> 00:24:27.539 spectacle. It was stage drama. Pasteur accepted 00:24:27.539 --> 00:24:30.019 a public challenge from a local veterinary society. 00:24:30.400 --> 00:24:34.420 The setup was highly visible. 58 sheep, 2 goats, 00:24:34.539 --> 00:24:37.440 and 10 cattle. Half were vaccinated with his 00:24:37.440 --> 00:24:39.940 attenuated culture. The other half, the control 00:24:39.940 --> 00:24:42.740 group, remained unvaccinated. And then came the 00:24:42.740 --> 00:24:46.859 climax. On May 31st, all 70 animals, vaccinated 00:24:46.859 --> 00:24:50.000 and untreated, were injected with a highly virulent, 00:24:50.000 --> 00:24:52.940 fresh culture of anthrax. And the world waited. 00:24:53.390 --> 00:24:55.730 The public observation on June 2nd must have 00:24:55.730 --> 00:24:57.490 been incredible. It was a shattering success. 00:24:57.769 --> 00:24:59.809 The untreated animals were either dead or dying 00:24:59.809 --> 00:25:01.730 scattered across the field. All the vaccinated 00:25:01.730 --> 00:25:04.230 animals survived, showing no symptoms at all. 00:25:04.329 --> 00:25:06.730 The press went wild. Pasteur became an instant 00:25:06.730 --> 00:25:09.029 global hero. He did. And he seemed to confirm 00:25:09.029 --> 00:25:11.309 his claim that this was a superior live vaccine 00:25:11.309 --> 00:25:13.670 compared to anything that came before. But this 00:25:13.670 --> 00:25:15.529 is where we encountered the ethical complexity 00:25:15.529 --> 00:25:17.869 that defines his legacy. Because he wasn't being 00:25:17.869 --> 00:25:20.400 entirely truthful about his methods. He publicly 00:25:20.400 --> 00:25:22.920 insisted this was a live, attenuated vaccine, 00:25:23.140 --> 00:25:25.839 which allowed him to dismiss prior work by his 00:25:25.839 --> 00:25:29.259 rivals. Specifically, a veterinary surgeon named 00:25:29.259 --> 00:25:32.279 Henri Toussaint had developed a functional anthrax 00:25:32.279 --> 00:25:36.240 vaccine in 1880 using heat -killed bacilli. And 00:25:36.240 --> 00:25:38.960 Pasteur publicly contested his results. He did. 00:25:39.099 --> 00:25:41.220 He claimed a killed vaccine wouldn't provide 00:25:41.220 --> 00:25:44.220 lasting immunity. But the truth, which came out 00:25:44.220 --> 00:25:46.839 much later from his notebooks, complicates this 00:25:46.839 --> 00:25:49.390 story. What did the notebooks reveal? Historian 00:25:49.390 --> 00:25:51.369 Gerald Geisen's analysis confirmed that for that 00:25:51.369 --> 00:25:53.730 specific public demonstration at Puy -le -Fort, 00:25:53.930 --> 00:25:56.950 Pasteur and Chamberlain secretly used a potassium 00:25:56.950 --> 00:25:59.920 dichromate killed vaccine. a chemical method 00:25:59.920 --> 00:26:02.259 conceptually very similar to Toussaint's approach. 00:26:02.480 --> 00:26:05.440 So he deliberately misled everyone. He misled 00:26:05.440 --> 00:26:07.680 the public and the scientific community about 00:26:07.680 --> 00:26:10.279 the methods used in that celebrated trial to 00:26:10.279 --> 00:26:12.839 guarantee success and to defeat his rivals. It 00:26:12.839 --> 00:26:15.700 raises such profound questions about means and 00:26:15.700 --> 00:26:18.920 ends. He achieved a world -saving result, but 00:26:18.920 --> 00:26:21.799 the method for securing public trust. It relied 00:26:21.799 --> 00:26:24.500 on a degree of professional deception. The rabies 00:26:24.500 --> 00:26:26.740 work represents the final and I think the most 00:26:26.740 --> 00:26:29.440 high stakes application of Pasteur's methods. 00:26:29.819 --> 00:26:32.339 Rabies was a uniquely terrifying death sentence 00:26:32.339 --> 00:26:35.319 in the 19th century. Incurable, gruesome, and 00:26:35.319 --> 00:26:38.099 virtually 100 % fatal once symptoms appeared. 00:26:38.279 --> 00:26:41.140 Just horrific. His approach to creating the vaccine 00:26:41.140 --> 00:26:43.920 was novel, mostly because rabies is a virus and 00:26:43.920 --> 00:26:46.180 they couldn't culture viruses like bacteria back 00:26:46.180 --> 00:26:49.279 then. So how did they prepare it? They used a 00:26:49.279 --> 00:26:52.460 process called passage. They would grow the rabies 00:26:52.460 --> 00:26:55.099 virus in rabbits, passing the infection from 00:26:55.099 --> 00:26:57.279 one rabbit to the next until they had a strain 00:26:57.279 --> 00:27:00.460 with a consistent incubation period. Then they 00:27:00.460 --> 00:27:02.500 would harvest the affected nerve tissue, the 00:27:02.500 --> 00:27:05.059 spinal cord specifically, and hang strips of 00:27:05.059 --> 00:27:07.789 it in a sterilized dry container. The exposure 00:27:07.789 --> 00:27:10.170 to air and desiccation would gradually weaken 00:27:10.170 --> 00:27:12.650 or attenuate the virus over a period of days. 00:27:12.829 --> 00:27:14.930 So the longer the tissue dried, the weaker the 00:27:14.930 --> 00:27:17.569 virus became. This let him create a sort of scale 00:27:17.569 --> 00:27:20.170 of attenuation. Yes, a sliding scale from the 00:27:20.170 --> 00:27:22.690 least virulent, the oldest, most dried tissue, 00:27:22.809 --> 00:27:25.150 to the most virulent, which was the newest, least 00:27:25.150 --> 00:27:27.289 dried tissue. And that system was absolutely 00:27:27.289 --> 00:27:29.789 critical for the famous first human trial. The 00:27:29.789 --> 00:27:32.349 trial of nine -year -old Joseph Meister in July 00:27:32.349 --> 00:27:36.500 1885. He had been severely mauled by a rabid 00:27:36.500 --> 00:27:40.359 dog and was facing near certain death. The decision 00:27:40.359 --> 00:27:43.019 to intervene must have been excruciating. It 00:27:43.019 --> 00:27:46.559 was an unimaginable risk. Pasteur, along with 00:27:46.559 --> 00:27:49.019 the boy's mother, decided to go ahead. The treatment 00:27:49.019 --> 00:27:51.500 was complex and aggressive. Meister received 00:27:51.500 --> 00:27:55.029 13 inoculations over 11 days. And the procedure 00:27:55.029 --> 00:27:57.269 involved starting with the most attenuated virus 00:27:57.269 --> 00:27:59.609 and progressively getting stronger. Exactly. 00:27:59.609 --> 00:28:02.009 Start with the safest, most weakened nerve tissue 00:28:02.009 --> 00:28:04.150 and then inject cultures that were less and less 00:28:04.150 --> 00:28:06.529 attenuated, moving toward the most virulent strains 00:28:06.529 --> 00:28:08.730 by the end of the treatment. The idea was to 00:28:08.730 --> 00:28:11.069 give Meister's immune system time to build protection 00:28:11.069 --> 00:28:13.369 against the weak virus before introducing the 00:28:13.369 --> 00:28:15.650 stronger ones. Right. And the outcome was one 00:28:15.650 --> 00:28:17.809 of the great medical miracles of the century. 00:28:18.109 --> 00:28:20.740 Joseph Meister recovered completely. And the 00:28:20.740 --> 00:28:23.519 world immediately hailed Pasteur as a humanitarian 00:28:23.519 --> 00:28:27.799 hero, a figure comparable to Jenner. But retrospectively, 00:28:27.799 --> 00:28:29.559 and especially after the notebooks were revealed, 00:28:29.799 --> 00:28:32.339 the ethical complexity of that decision really 00:28:32.339 --> 00:28:34.859 came into sharp focus. What were the main criticisms 00:28:34.859 --> 00:28:38.099 that emerged? The first, and most obvious, was 00:28:38.099 --> 00:28:41.220 that Pasteur was not a licensed physician. He 00:28:41.220 --> 00:28:43.799 was risking prosecution for practicing medicine 00:28:43.799 --> 00:28:46.900 without a license. A huge personal risk. A huge 00:28:46.900 --> 00:28:50.039 risk. And crucially, his highly skilled medical 00:28:50.039 --> 00:28:53.240 partner, Emile Roux, refused to participate in 00:28:53.240 --> 00:28:55.779 the clinical trial. He argued that the vaccine 00:28:55.779 --> 00:28:58.160 was not yet sufficiently tested or standardized 00:28:58.160 --> 00:29:01.359 for human application. Roux's refusal really 00:29:01.359 --> 00:29:04.240 underlines how premature the experiment was perceived 00:29:04.240 --> 00:29:06.619 to be. The second major issue was the preliminary 00:29:06.619 --> 00:29:10.319 testing. Pasteur... publicly claimed he had successfully 00:29:10.319 --> 00:29:12.980 vaccinated 50 dogs. Which would have been a pretty 00:29:12.980 --> 00:29:15.859 robust preclinical trial. However, the private 00:29:15.859 --> 00:29:18.019 notebooks tell a different story. They suggest 00:29:18.019 --> 00:29:20.980 he had actually only vaccinated 11 dogs, and 00:29:20.980 --> 00:29:22.680 the results of those few trials were inconsistent. 00:29:23.119 --> 00:29:25.339 So the human application was based on far less 00:29:25.339 --> 00:29:27.940 data than he publicly admitted. Far less. He 00:29:27.940 --> 00:29:30.400 later defended the secrecy by saying it was necessary 00:29:30.400 --> 00:29:33.240 to control quality, but it fueled deep suspicion. 00:29:33.539 --> 00:29:35.799 But what about oversight? Was he entirely alone 00:29:35.799 --> 00:29:38.019 in performing the procedure? No, and that's a 00:29:38.019 --> 00:29:40.980 key mitigating factor. He consulted with two 00:29:40.980 --> 00:29:43.859 renowned practicing physicians, Jacques -Joseph 00:29:43.859 --> 00:29:47.180 Grancher and Alfred Volpian. And it was Grancher, 00:29:47.279 --> 00:29:49.859 the physician, who physically administered the 00:29:49.859 --> 00:29:52.880 13 injections to Meister. So while Pasteur conceived 00:29:52.880 --> 00:29:55.079 and erected the treatment, the actual inoculation 00:29:55.079 --> 00:29:57.670 was performed under medical oversight. which 00:29:57.670 --> 00:29:59.890 likely helped protect him from legal repercussions. 00:30:00.289 --> 00:30:03.569 But the decision, the moral and professional 00:30:03.569 --> 00:30:07.269 burden of it, was entirely his own. And the case 00:30:07.269 --> 00:30:10.190 highlights this immense personal urgency driving 00:30:10.190 --> 00:30:12.430 his work, which, as we'll see, was terribly, 00:30:12.430 --> 00:30:14.750 terribly personal. That personal urgency is so 00:30:14.750 --> 00:30:17.450 crucial. Before we dive into the rivalries that 00:30:17.450 --> 00:30:19.529 haunted his professional life, let's just reflect 00:30:19.529 --> 00:30:21.950 on the personal stakes. Pasteur and his wife 00:30:21.950 --> 00:30:24.650 Marie had five children. But devastatingly, three 00:30:24.650 --> 00:30:27.039 of them died in childhood. mostly from typhoid 00:30:27.039 --> 00:30:29.400 fever. It's impossible to separate that staggering 00:30:29.400 --> 00:30:31.700 personal loss from his almost feverish drive 00:30:31.700 --> 00:30:35.140 to conquer infectious disease. Absolutely. Typhoid 00:30:35.140 --> 00:30:38.519 is a classic waterborne microbial disease. To 00:30:38.519 --> 00:30:41.019 lose three children to the very microscopic world 00:30:41.019 --> 00:30:43.599 he was trumped to conquer. It must have imbued 00:30:43.599 --> 00:30:47.180 his entire career with this profound, relentless 00:30:47.180 --> 00:30:50.160 mission. And that relentless ambition often came 00:30:50.160 --> 00:30:52.420 into conflict with other scientists, especially 00:30:52.420 --> 00:30:55.059 once the veil of secrecy around his work was 00:30:55.059 --> 00:30:57.339 lifted with the publication of his lab notebooks. 00:30:57.680 --> 00:31:00.589 The story of the notebooks is fascinating. Pasteur 00:31:00.589 --> 00:31:03.369 insisted his family never reveal them. They were 00:31:03.369 --> 00:31:06.950 held privately until 1971, nearly a century after 00:31:06.950 --> 00:31:09.329 his birth. And when historian Gerald L. Geisen 00:31:09.329 --> 00:31:12.549 finally published his analysis in 1995, it was 00:31:12.549 --> 00:31:15.630 a bombshell. It confirmed long -held suspicions. 00:31:15.730 --> 00:31:18.109 The Pasteur had systematically used deception, 00:31:18.410 --> 00:31:20.470 selective reporting, and misleading accounts 00:31:20.470 --> 00:31:23.190 to triumph over his rivals and secure priority. 00:31:23.630 --> 00:31:25.910 So let's break down the major scientific disputes 00:31:25.910 --> 00:31:28.230 that these revelations confirmed, starting with 00:31:28.230 --> 00:31:30.849 the rivalry in fermentation with Antoine Béchamp. 00:31:30.970 --> 00:31:32.769 Béchamp, he's a French physician and chemist 00:31:32.769 --> 00:31:34.930 who definitely deserves a strong mention. As 00:31:34.930 --> 00:31:37.769 early as 1858, Béchamp had claimed priority for 00:31:37.769 --> 00:31:39.950 showing the role of microorganisms in fermentation. 00:31:40.349 --> 00:31:42.789 He argued it was a living process before Pasteur 00:31:42.789 --> 00:31:46.269 published on it. He did. And he criticized Pasteur's 00:31:46.269 --> 00:31:48.529 methods and claims throughout his career. But 00:31:48.529 --> 00:31:52.160 Béchamp is largely forgotten today. Why did Pasteur 00:31:52.160 --> 00:31:55.480 win that historical argument? Well, Bechamp certainly 00:31:55.480 --> 00:31:58.259 had valid points about priority. But he later 00:31:58.259 --> 00:32:00.519 went off the rails by developing this complex 00:32:00.519 --> 00:32:03.660 and ultimately incorrect microzymes theory. He 00:32:03.660 --> 00:32:06.019 believed all living things were composed of these 00:32:06.019 --> 00:32:08.859 tiny, indestructible molecular granules that 00:32:08.859 --> 00:32:11.240 could transform into bacteria. Okay, that sounds 00:32:11.240 --> 00:32:13.339 a bit out there. It was a flawed theoretical 00:32:13.339 --> 00:32:16.700 framework. And it allowed Pasteur... who focused 00:32:16.700 --> 00:32:20.240 on simple, demonstrable microbial action to sideline 00:32:20.240 --> 00:32:23.500 him and cement his own reputation. Pasteur was 00:32:23.500 --> 00:32:25.859 ruthless in not citing or acknowledging work 00:32:25.859 --> 00:32:28.759 that might dilute his own claim. The other, perhaps 00:32:28.759 --> 00:32:31.000 more damaging rivalry was the one with Henri 00:32:31.000 --> 00:32:33.240 Toussaint over the anthrax vaccine. It was a 00:32:33.240 --> 00:32:35.859 bitter dispute. As we said, Toussaint developed 00:32:35.859 --> 00:32:38.900 the first effective anthrax vaccine in 1880 using 00:32:38.900 --> 00:32:42.140 heat -killed bacilli. Pasteur publicly disparaged 00:32:42.140 --> 00:32:44.759 this concept, arguing a dead vaccine couldn't 00:32:44.759 --> 00:32:47.259 provide lasting immunity. And yet his notebooks 00:32:47.259 --> 00:32:49.539 showed that his celebrated Pouilly Four trial 00:32:49.539 --> 00:32:53.039 used a chemically killed vaccine which operated 00:32:53.039 --> 00:32:55.680 on the same principle as Toussaint's. It was 00:32:55.680 --> 00:32:58.880 a massive public victory, won by secretly borrowing 00:32:58.880 --> 00:33:01.440 from his rival's concept without ever providing 00:33:01.440 --> 00:33:04.759 attribution. It really highlights the intense 00:33:04.759 --> 00:33:07.539 pressure for priority and recognition in 19th 00:33:07.539 --> 00:33:09.980 century science. And we can't ignore the methodological 00:33:09.980 --> 00:33:13.400 clashes with Robert Koch, the great German microbiologist. 00:33:13.700 --> 00:33:15.940 That was less about priority and more about a 00:33:15.940 --> 00:33:18.480 difference in scientific philosophy. Koch, who 00:33:18.480 --> 00:33:20.880 had identified the anthrax bacterium and developed 00:33:20.880 --> 00:33:24.059 his famous postulates, was meticulous. He criticized 00:33:24.059 --> 00:33:26.380 Pasteur's use of impure cultures and imprecise 00:33:26.380 --> 00:33:29.049 protocols. And Pasteur's response? He defended 00:33:29.049 --> 00:33:31.630 his results robustly, sometimes accusing Koch 00:33:31.630 --> 00:33:34.650 of misinterpreting data. This rivalry drove both 00:33:34.650 --> 00:33:37.430 men to massive breakthroughs. Koch focused on 00:33:37.430 --> 00:33:40.069 isolation and pure culture, while Pasteur focused 00:33:40.069 --> 00:33:42.890 on physiological manipulation, like attenuation. 00:33:43.329 --> 00:33:45.549 Finally, let's consider his institutional legacy 00:33:45.549 --> 00:33:48.150 and his personal faith. There's a lasting debate 00:33:48.150 --> 00:33:50.369 over whether he remained a devout Catholic or 00:33:50.369 --> 00:33:53.049 became more of a spiritual freethinker. His family 00:33:53.049 --> 00:33:55.609 presented conflicting pictures. His son -in -law 00:33:55.609 --> 00:33:58.920 said Pasteur had absolute faith in God. But his 00:33:58.920 --> 00:34:01.299 grandson later noted that Pasteur retained only 00:34:01.299 --> 00:34:03.940 a sort of spiritualism without formal religious 00:34:03.940 --> 00:34:06.960 practice. And Pasteur himself. He was a strong 00:34:06.960 --> 00:34:09.500 advocate for the separation of science and dogma. 00:34:09.559 --> 00:34:12.559 He famously said, woe to those who want to make 00:34:12.559 --> 00:34:15.320 them encroach upon one another. He was a man 00:34:15.320 --> 00:34:18.159 of deep contemplation, but he fiercely guarded 00:34:18.159 --> 00:34:21.110 the independence of scientific inquiry. Regardless 00:34:21.110 --> 00:34:23.389 of his personal beliefs, his institutional legacy 00:34:23.389 --> 00:34:25.929 is absolutely undisputed. The success of the 00:34:25.929 --> 00:34:28.389 rabies vaccine led to massive global fundraising. 00:34:28.690 --> 00:34:30.510 And that fundraising led to the establishment 00:34:30.510 --> 00:34:33.969 of the Pasteur Institute in 1887. Its initial 00:34:33.969 --> 00:34:36.539 purposes were to provide rabies treatment. and 00:34:36.539 --> 00:34:39.139 be a fundamental research hub for virulent diseases. 00:34:39.559 --> 00:34:41.980 It immediately drew top scientific talent. It 00:34:41.980 --> 00:34:45.119 did, including Émile Roux, who, despite his ethical 00:34:45.119 --> 00:34:47.400 concerns about the Meister trial, established 00:34:47.400 --> 00:34:49.920 the world's first formal course in microbiology 00:34:49.920 --> 00:34:52.340 there. And today, the institute is this vast 00:34:52.340 --> 00:34:56.400 international network, 32 institutes in 29 countries, 00:34:56.539 --> 00:34:59.119 continuing the work he pioneered. It's the ultimate 00:34:59.119 --> 00:35:02.579 testament to his impact, as the French academician 00:35:02.579 --> 00:35:06.219 Henri Mondor summarized it so eloquently. Louis 00:35:06.219 --> 00:35:08.599 Pasteur was neither a physician nor a surgeon, 00:35:08.719 --> 00:35:11.159 but no one has done as much for medicine and 00:35:11.159 --> 00:35:13.679 surgery as he has. An industrial chemist who 00:35:13.679 --> 00:35:17.480 became medicine's greatest champion. That was 00:35:17.480 --> 00:35:20.139 an extraordinary life to unpack. We've traveled 00:35:20.139 --> 00:35:22.619 from a painstaking experiment proving molecular 00:35:22.619 --> 00:35:25.579 asymmetry, a cornerstone of modern chemistry, 00:35:25.719 --> 00:35:28.199 all the way through to establishing public health 00:35:28.199 --> 00:35:31.000 standards with pasteurization. And settling the 00:35:31.000 --> 00:35:33.539 ancient debate of spontaneous generation with 00:35:33.539 --> 00:35:35.960 the swan -necked slask. And pioneering the entire 00:35:35.960 --> 00:35:38.599 age of artificial vaccination against killers 00:35:38.599 --> 00:35:41.199 like anthrax and rabies. His foundational work 00:35:41.199 --> 00:35:43.929 is the bedrock of modern life. Every time you 00:35:43.929 --> 00:35:46.349 use sterile medical equipment, drink safe milk, 00:35:46.409 --> 00:35:48.829 or rely on a vaccine, you are leveraging the 00:35:48.829 --> 00:35:51.130 principles established by his relentless efforts. 00:35:51.369 --> 00:35:53.849 The invisible world he made visible defines our 00:35:53.849 --> 00:35:56.349 existence today. It really does. So as you reflect 00:35:56.349 --> 00:35:58.449 on this extraordinary legacy, we want to leave 00:35:58.449 --> 00:36:00.389 you with the challenging ethical question that 00:36:00.389 --> 00:36:02.610 the revelation of his notebooks forces us to 00:36:02.610 --> 00:36:05.639 confront. Pasteur, driven by ambition and this 00:36:05.639 --> 00:36:07.639 fierce desire to see his discoveries adopted 00:36:07.639 --> 00:36:10.760 quickly, used methods of secrecy and selective 00:36:10.760 --> 00:36:13.239 reporting to outmaneuver rivals like Toussaint 00:36:13.239 --> 00:36:16.139 and Béchamp. Those methods, judged by modern 00:36:16.139 --> 00:36:19.440 scientific standards, they lack integrity. Yet 00:36:19.440 --> 00:36:21.739 they led directly to breakthroughs like the functional 00:36:21.739 --> 00:36:23.840 anthrax vaccine and the successful treatment 00:36:23.840 --> 00:36:26.940 of Joseph Meister, saving untold millions of 00:36:26.940 --> 00:36:30.159 lives. So how, then, should history ultimately 00:36:30.159 --> 00:36:33.469 judge the man? If a scientist's ethical shortcuts 00:36:33.469 --> 00:36:36.190 lead directly to world -saving breakthroughs, 00:36:36.210 --> 00:36:38.949 is the resulting immense benefit always sufficient 00:36:38.949 --> 00:36:41.210 justification for the methods they use? It's 00:36:41.210 --> 00:36:43.789 the tension between scientific progress and personal 00:36:43.789 --> 00:36:45.909 integrity. And it's a question that continues 00:36:45.909 --> 00:36:47.929 to challenge the moral landscape of scientific 00:36:47.929 --> 00:36:50.269 advancement today. Something to consider the 00:36:50.269 --> 00:36:52.449 next time you see that name printed on your food 00:36:52.449 --> 00:36:54.670 packaging. That was the Deep Dive. We'll see 00:36:54.670 --> 00:36:55.090 you next time.