The Germ Theory of Disease

  Prof: Well good morning.  I think we should get started.  And what we'll be talking aboutthis morning is the germ theory of disease.  In a sense, it's taken us halfa course to reach a period when we begin to see the developmentof what you would probably recognize as a scientific modernmedicine. To appreciate the enormity ofwhat happened with the germ theory of disease,I think it's worth casting our eye back to a point we hadalready reached. Let's say we compared the year1789 with 1900. Before 1789,and the developments with the Paris School of Medicine,you'll remember the conceptual framework was dominated,still, by that of Hippocrates, Galen and humoral medicine.  Humoralism was in retreat,as doctors were absorbing ideas about the circulatory system,and the nervous system. But the medical philosophy,the vocabulary, therapeutics and medicaleducation, were still cast in the oldframework, supplemented by otherdevelopments-- astrology, for example--andepidemic diseases were thought to be explained by the doctrineof miasma-- that is, the corruption orpoisoning of the air-- or malaria, as it was called atthe time. By 1900, I think it's clearthat more change had occurred than in all of the centuriessince Hippocrates combined, and that medical science,whose basic principles were recognizably similar to our owntoday, had emerged.  Furthermore,the speed of change was gathering momentum as thenineteenth century progressed. The closing decades of thecentury witnessed a wholesale revolution, with the germ theoryof disease as its central feature.  This theory,I'm going to argue, was as important a revolutionin medicine as for, example, Galileo's theory ofthe rotation of the earth was to astronomy;or perhaps Darwin's theory of natural selection was tobiology; or gravitation to physics.  So, what I would like to beginwith then is looking at what is the germ theory?  What were its preconditions?  Who were the decisive figures?  What were the decisive eventsassociated with that famous trio of Louis Pasteur,Joseph Lister, Robert Koch?  What were the implications?  Let's avoid the idea of asingle genius coming up with a great idea.  Let's question the visionbehind the idea of the Nobel Prize.  I'm going to be arguing thatthese discoveries, that culminate in the germtheory, had a long gestation period,and were a collective process that required a long train ofpreconditions. Let's look at the preconditionsfirst. I'll argue that they'reconceptual, technological and institutional.  Let's look at conceptualpreconditions. The germ theory of diseasedidn't arise directly out of hospital medicine and the ParisSchool, but I think it's inconceivablewithout the background of that development.  It was crucial to have anosology--that is, disease classification--theidea of disease specificity-- that they were specificentities--and without the idea of localism;that is, lesions. And also essential was the newdevelopment of pathological anatomy, derived from thepost-mortem in the Paris hospitals.  The idea of specificity wascritical. Any further progress to theidea of a microbial disease depended on the view thatdiseases didn't transform from one into another.  Before the Paris School,it was common to believe, for example,that cholera--to take one disease--was simply a heightened form of endemic summer diarrhea.  It wasn't a specific disease,and it grew out of another preexisting condition.  The germ theory dependedinstead on the conviction that there are stable,unchanging disease entities, that each one is specific andhas a specific microbial cause. But the followers ofLouis--Pierre Louis, that is--in Paris,while carefully distinguishing one disease from another,and classifying them, didn't advance much towards theidea of the causative pathogens behind them.  Now, when we've talked aboutthe Paris School, I don't want to give you theidea that all of the crucial figures in disease specificity,and nosology, were French. There were other crucialfigures as well. William Gerhard,who distinguished typhus from typhoid.  He had studied in Paris withLouis for a couple of years, and then returned to his nativePhiladelphia. During an epidemic of typhus,he dissected hundreds of cadavers and discovered thattheir lesions had no resemblance whatsoever to typhoid.  There was William Budd,who wrote an important book called Typhoid Fever:Its Nature, Mode of Spreading and Prevention,in 1873. And he referred to theunchanging, specific nature of the disease.  Let's listen to what he said.  He said this:"To propagate itself and no other,and that on a series of indefinite progressions,constitutes the very essence of the relation on which the ideaof species is founded. How much this applies in theanimal and plant world we all know.  It is strange that what itimplies, in the case of diseases, should be so seldomrecognized until now." Or there was Pierre Bretonneau,who believed that there were morbid seeds that caused specialdiseases, just as every seed--in thenatural history, that is--gives rise to adetermined species. And he applied that idea todiphtheria. Just so as apples don't turninto wheat--apples seeds into wheat--so too endemic diarrheadoesn't transform itself into Asiatic cholera.  There was an importanttransitional figure too. Claude Bernard,of the Paris School, one of its stars,who lived from 1813 to 1878, and in 1865 wrote an importantbook called An Introduction to the Study of ExperimentalMedicine, where he presented a critiqueof the Paris School. He argued that diseases weredynamic processes. They weren't static in the waythat the Paris idea of nosology seemed to suggest.  And he argued that they,hospitals, displayed the end stages of diseases,not their beginnings. And he argued that hospitalsand clinics had an excess of variables that wasn't helpfulfor the further development of medical science.  So, he proposed an alternative,that was embodied in his title; that is, experimental medicine.  And by that,he meant laboratory medicine. He's one of the people whosuggest a new epistemology for medicine,which isn't the hospital ward but the lab,where you could have the experimental testing of singlevariables in controlled settings.  Here was a new source ofmedical knowledge. If that provides conceptualpreconditions, there were also institutionalones. And here I'm thinking of therise of the laboratory, of the university;that is, full-time professional scientists, researchinstitutions, and Germany leading the way,rather than France, in this development.  There were also technologicalfoundations. It's impossible to think of therise of the germ theory of disease without microscopy.  And so it was indebted to Antonvan Leeuwenhoek, who lived from 1632 to 1723,and developed the simple microscope.  And then in the 1820s,and thereafter, there were major improvements:the development of the compound microscope and highermagnification, the work of the Zeiss Companyand the development of lenses. There was also,for a fourth precondition, a lonely, neglected pioneer,and that was a Hungarian gynecologist,who lived in Vienna, called Ignaz PhillipSemmelweis, whose crucial idea,which dates from the 1840s-- Semmelweis noted that theinfection rate in childbirth was much lower on obstetrical wardswhere women were delivered by midwives,rather than on wards where they were delivered by physicians.  The reason had nothing to dowith their training or relative degree of benevolence andmalevolence. The point was that thephysicians were just returning from post-mortem examinations,from autopsies, after which,at that time, they didn't wash their hands,and so they were transmitting disease to their patients,from autopsies they were performing in an adjacentbuilding. So, Semmelweis,suspecting--although he didn't know the mechanism--that this was the case, established elaboratehand-washing rituals, using a chlorinated limesolution--a little bit the first hand sanitizer,we might say--and he noted that mortality plummeted from twentypercent to one percent. Unfortunately,his own career was not a happy one.  He was mocked by his colleaguesas a charlatan, and was actually demoted in hisown hospital. Well, then, there's a fifthprecondition, and that's the development ofthe basic sciences. And it's hard to imagine,as we'll see in a minute, the rival of the germ theorywithout chemistry in particular. The specific issue that gaverise to the germ theory of disease was fermentation.  And Pasteur,after all, was originally a chemist, who in the 1860s becamea biologist, and we should note that he wasn't a physician.  This is to introduce you toLouis Pasteur. The immediate background to thegerm theory of disease involved the dominant theory of the day,which was called the zymotic theory of disease;that is, that it was a form of ferment--a little bit likePettenkofer had asserted--caused by some fermentation of decayingorganic material. Under the right conditions ofsoil, temperature and moisture, this fermentation would giveoff a poison into the environment.  Also quite widespread was theidea of spontaneous generation, that diseases arose somehowspontaneously in a particular locality,weren't brought in or imported from the outside.  There was a famous experimentabout this, from the seventeenth century.  It was Redi's maggot experiment.  The idea was that if you couldhave rotting meat, and you could cover it,you wouldn't develop maggots. But if you didn't cover it,then you would find that it was full of maggots.  So, the maggots didn't appearin the rotting meat by some internal mechanism ofspontaneous generation, but were imported from outside.  And Pasteur,as we'll see in a minute, takes up this very idea,to the idea that germs too, like the maggots,are imported from outside. The immediate issue for Pasteurwas in fact fermentation. He began by studying thefermentation of wine and beer, and in particular theirspoilage. At the time,this was thought, when he took up his work,to be a chemical process. And remember that Pasteur wasnot a physician but a chemist originally.  Well, what he did was todiscover that the fermentation was caused instead by livingmicroorganisms, bacteria that he identifiedthrough the microscope. Now, this was a high-profileinvestigation in the 1860s, for the simple reason that theproduction of wine and beer involved two of France's majoreconomic activities. Pasteur--and this was part ofhis genius--immediately made a far-reaching connection.  In his estimate,the fermentation that he saw in wine and beer,now caused by bacteria, was analogous to putrefactionand infection in wounds, for example.  So, he began to regard diseaseas a process involving microorganisms,living things. This was work that Pasteurconducted in the late 1850s and 1860s,and it marked the first transformation in his careerfrom that of a chemist into a biologist,or we might say today a microbiologist.  He examined not only wine andbeer, he then turned his attention tomilk and its souring, and he wrote a book on that,and then a study on wine and a study on beer.  Now, of great importance wasthe fact that Pasteur's discovery that abnormalfermentation leads to spoilage, along with that went anotherdiscovery he made, which was that this processcould be controlled by heat. Here was a major public healthdiscovery, and that led to the process we now know aspasteurization. So, already in the 1860s,Pasteur was busily transforming biology.  Even if had he stopped then,his discoveries were already those of a fully productivelife's work. But then in the 1860s came aturn in Pasteur's interests from biology, more specifically tomedicine and public health. And he began to studyspontaneous generation. Now, followers of Pasteurbelieved instead in biogenesis. With regard to cholera,that we already examined, about which there was a debate,the idea was that cholera was imported from outside.  It didn't arise spontaneously.  It wasn't the transformation ofsome other disease that already existed into cholera.  Rather it was a specificdisease that could not arise as a heightened form of apre-existing condition. Pasteur also devised--well,Koch didn't think this was so elegant,but it certainly convinced Pasteur and his followers--a famous swan neck flask experiment.  That is, he sterilized a flaskwith a swan's neck, and found that if the cultureis boiled, and the flask prevents air fromgaining access to it, then there was no developmentinside of organisms that we would call bacteria.  A culture of them could grow inthe flask, only if germs were allowed to enter it.  But if the neck of the flask isbroken and air is emitted--you can see the neck broken at thebottom--then you get a luxurious development of life.  And this had enormousimplications for diseases and wounds.  Pasteur wrote simply,"There is no known circumstance in which it can beconfirmed that microscopic beings came into the worldwithout germs, without parents similar tothemselves." Now, Pasteur's success waspartly based on the fact that he was aware of the full range ofthe scientific implications of his work,and he selected carefully topics with high profile,philosophical and biological interest.  He was an expert at cultivatingthe media. That was one reason thatspontaneous generation had led to so much excitement.  But most decisive in Pasteur'swork was what he did in the 1870s,as he turned to diseases, demonstrating the fullimplications of his ideas on fermentation in the previousdecade. This new phase of discoveryoccurred, despite the fact that in 1868he suffered a major cerebral hemorrhage,that left him paralyzed on his left side.  What did Pasteur do in the1870s that was so crucial? Well, first of all,I'll look at two major things that he did.  One is work with silkworms,and the other is work with chicken cholera and anthrax.  The first thing was a majorcontribution to the germ theory of disease, accomplished by thework with an unexpected experimental animal;that is, the silkworm. And again let's look at thefact that Pasteur's success, his influence and his genius,was in part the fact that he took on really high-profileresearch topics; that is to say,disease of silkworms, where these diseases weredecimating one of France's leading industries,that is, silk. Through meticulous andpainstaking research, Pasteur demonstrated that therewere two major diseases at work affecting France's silkworms.  He called them pebrine andflacherie--you needn't remember them for our purposes--andasserted that both were specific diseases caused by bacteria.  And he immediately realizedthat there were enormous implications,not only for silkworms, but for human beings as well.  He isolated then two germsaffecting silkworms, and demonstrated that they wereresponsible for specific contagious diseases.  Pasteur isolated a germ andconvincingly linked it with a specific disease,and the concept of specificity was at the basis then of thewhole idea of the germ theory of disease.  Now you know Pasteur didn'tinvent the idea of contagion. You've seen it with Fracastoro.  You've seen it in John Snow,who talked about the possibility of animalcules.  And there were otherscientists--Casimir Devaine in France,the English physician John Sanderson--who were also advancing a hypothesis that they werefinding microbes with their microscopes,and hypothesizing that they might be the agents of disease.  But Pasteur was the first toprovide a demonstration in a specific case,proving that microbes were the causative agents of specificdiseases, and he provided a methodologyfor further experimentation and discovery.  Pasteur then turned fromsilkworms to diseases, the diseases of chicken choleraand anthrax. Neither is responsible forextensive human disease, as both are causes of diseasesof animals. But what was critical was theprocess. His work on anthrax helped toestablish a model for investigating infectiousdiseases, and establishing the claims forthe germ theory of disease, and putting that on solidfoundation. At the same time,he made another major development.  His vision went beyond simplydemonstrating the germ theory, although he did that.  In addition,he developed a public health practice--that is, vaccination, which had been pioneered ahundred years before-- and he helped now to found thediscipline of experimental immunology.  Now, let's--we've seenvaccination and the work of Edward Jenner.  Let's define.  Vaccination is the introductioninto the body of either the whole,or part, of a disease-causing microorganism,in order to teach the immune system to attack that sameorganism, should it reappear in the bodythrough natural processes. The mechanism is that thevaccine primes the immune system to produce antibodies,or teaches immune cells to recognize and attack theorganism, that we now know perhaps to bea virus, a bacterium,or a parasite of a different kind.  The problem,of course, was how to stimulate immunity without causingdisease. Jenner benefited from thecross-over immunity from cowpox to smallpox.  Pasteur did something else.  He used the concept ofattenuation. Jenner is the father ofimmunology, in a sense, Pasteur the founder ofexperimental immunology. The idea he had was that livepathogens could be introduced in the body,but only after being treated in some way--heat, for example, or passage through a differenthost first was another-- in such a way then that theirvirulence is diminished. Then they'll stimulate theimmune response, without causing disease at all,or only a mild disease. This discovery was made duringhis work with the bacterium that causes chicken cholera,made sort of by chance--serendipity played arole. He left a batch of bacteriauntouched for a week or so while he went on vacation during thehot summer months. On returning,he found initially, to his frustration,that the culture no longer produced the disease when heattempted to infect other chickens.  So, he got a fresh batch ofbacterium, and injected the same chickens with it,as well as a lot of new chickens, and made a surprisingdiscovery. That the original chickens,injected with the old vaccine, remained healthy--in our terms,they were immune-- while the new and previouslyuntreated chickens sickened and died.  He repeated the experimentseveral times, with the same results,and concluded that the summer heat had changed or attenuatedthe culture of the bacterium. Later techniques expanded therepertoire, demonstrating that heat could kill vaccines ofchicken cholera but still induce immunity.  There were other vaccines thatcould employ live but attenuated bacteria or viruses.  Some used killed microorganisms.  Some used sub-unit vaccines.  And the processes ofattenuation are not only heat, but let's say for polio,could be the passage through formaldehyde and various--there are other means. Attenuation though was criticalto the development of vaccine as a public health strategy.  But let's return to Pasteur.  Having discovered attenuationwith chicken cholera, Pasteur applied the sameprinciple to the different disease of anthrax.  The pathogen responsible wasthe Bacillus anthracis that had recently been isolatedby Robert Koch. And if you see the film,The Story of Louis Pasteur, you'll see what hedid in 1881 with the bacterium. In a famous experiment,he vaccinated twenty-four sheep with an attenuated--that is, heated--bacterium, after which he challenged theoriginal twenty-four sheep with live unattenuated anthraxinjections, as well as twenty-four controlsheep that had not been vaccinated.  The vaccinated sheep remainedhealthy. The non-vaccinated all died.  Then came the 1880s,and Pasteur turned to another high profile disease,and that is rabies. Having discovered attenuationby heat, with chicken cholera and anthrax, Pasteur extendedthe principle of attenuation by other means.  This involved further famousexperiments. Rabies, as it turns out,was not another bacterial disease, but a disease caused bywhat we now know to be a virus. In this case,he attenuated the virus by isolating it from foxes,and then passing it through an unnatural host of a differentspecies; in this case, the rabbit.  So, passing the virus through aseries of rabbit bodies, he succeeded in producing avariant that would no longer cause the infection in foxes,but would serve to protect against the natural occurringrabies. Rabies was not a high impactdisease, in terms of numbers of peopleit affected, but it was a disease of highdrama, and one that was then,and still is, universally fatal.  So, it was ideal for attractingmedia attention. The great human trial occurredin July 1885, with a famous case of anine-year-old boy, Joseph Meister,who had been severely bitten by a rabid dog and was thought tobe certain to die an agonizing death.  But taking advantage of theincubation period for rabies, Pasteur vaccinated the boy withhis attenuated rabies virus. Joseph Meister survived,and became a celebrity patient, the first person ever known tohave survived after being severely bitten by a rabidanimal. And Meister remained loyal forthe rest of his life, to Pasteur.  He returned,as an adult, to Paris, to work as agatekeeper at the Pasteur Institute, where Pasteur himselfwas buried in the crypt. The apocryphal story--I won'tassert its truth-- the story is that he was killedin 1940, as an elderly man,when he tried to prevent occupying German troops fromdesecrating Pasteur's grave, the grave of a national icon ofan enemy power. A slightly less poignant butbetter documented narrative is that he committed suicide indespair of the German occupation.  Well, the PasteurInstitute--that's the vaccination of Joseph Meister.  It's not Pasteur doing theactual vaccination, because, as I said,he wasn't a physician. And this is the PasteurInstitute, founded in 1887,with Louis Pasteur himself as its first director,committed to biomedical research in Paris,and to a series of satellite institutes elsewhere in theworld. It followed the public healthstrategy of vaccination, pioneered by Jenner,and now consolidated by Pasteur.  The founding of thisinstitute--you'll note its size and imposing nature--gives us the opportunity to note in passing another aspectof nineteenth and twentieth century science.  The way in which it became afocal point for competing nationalisms,in a way familiar to us from the Cold War competition betweenthe U.S. and the USSR.  In any case,there's a clear case in the nineteenth century with therivalry between Louis Pasteur and Robert Koch,the embodiments and icons of French and German medicalscience, of two hostile national powers.  The Pasteur Institute in Parisrivaled the Koch Institute in Berlin.  And that brings us--we'll alsonote the crypt where Pasteur is buried.  There's a kind of--what shall Isay?--worship of Pasteur almost, and of French medical science.  But let's move on to RobertKoch, who lived from 1843 to 1910,the second great figure in the establishment of the germ theoryof disease, the German scientist who wastwenty years younger than Pasteur.  Now, if Pasteur's hallmark wasthe imaginative breadth of his scientific vision,Koch's distinctive feature was his scientific rigor,his more rigorous techniques of microbiology.  He had a critique,a famous critique, of the whole swan neck flaskexperiment. He argued that Pasteur had beenlucky--contamination was possible.  He developed the platetechnique, using the Petri dish and solid culture,and he developed staining techniques for microscopy.  What I'd particularly like youto note is his methodology, which he embodied in what arecalled "Koch's Postulates."  This was the methodology fordetermining that a suspected microbe is the causative agentof a particular disease. He said you could know thisunder four conditions. First, the organism suspectedas a pathogen must be found in all animals suffering from thedisease. In other words,it has to be universally present where the disease ispresent. And then the organism must beisolated from a diseased animal, and grown in culture.  Third, the cultured organismmust cause the disease, when introduced into a healthyanimal. And lastly, the organism mustbe re-isolated from the experimentally infected animal.  These postulates are some ofthe most famous in medical science, and were the model forestablishing germs as pathogens for other diseases.  Koch's microscopy had a numberof immediate implications. His staining raised the ideathat if you could stain, you could also have an idea ofmagic bullets, what later became antibiotics.  But Koch didn't pursue thatparticular interest. The other was this led toreliable differential diagnosis, and therefore a more properlybased nosology. It could lead also to majorpublic health measures, and ultimately to developmentsin therapeutics. It furthered the sanitary idea,and gave it a firm, scientific basis,and irrefutably proved the truth of contagionism ratherthan anticontagionism, as Pettenkofer learned,to his cost. But immediately therewasn't--it didn't imply, and I think we should notethis--the understanding of disease did not immediately leadto therapeutic advances. Remember what happened inNaples during the cholera of 1884.  Koch's idea was used for a verynegative therapeutic method; that is, acid enemas that wereadministered to patients. Well Koch also moved forward onother diseases, applying the methods he haddeveloped, that Pasteur had developed inthe 1870s, and applying his own rigorouspostulates. In 1882, the most famous ofall, he isolated the bacterium that causes tuberculosis,the most prevalent disease of the time.  The paper that Koch presentedin 1882 was one of the most dramatic and important momentsin the history of medicine. Tuberculosis was not feared inthe same way cholera was, but it was unquestionably thegreatest killer of the nineteenth century,and until 1882, it was shrouded in mystery.  Suddenly Koch cast a new shaftof life, revealing to the world that he had unraveled the entiremystery of its etiology. Then, in 1883,he followed up this discovery with another that was almostequally influential. In 1883, he isolated theVibrio cholerae. Koch then had discovered anddemonstrated the role of pathogens,the ones responsible for two of the most prevalent and fearednineteenth century diseases. This marked,as I said, the definitive triumph of contagionism.  And the 1880s and '90s were agolden age of microbiology, with the pathogens beingdiscovered for a whole range of other diseases.  This was an extraordinaryperiod in medical science. The pathogens were discoveredfor gonorrhea, bubonic plague,dysentery, tetanus, the common bacteria of woundinfections, staph infections and others.  The paradox,of course, there were still few benefits for patients,until the turn of the new century.  The quip was made that the mainbeneficiaries, at first, of the germ theory ofdisease, were physicians rather than patients.  But there was a majorexception, and that was not in medicine but in surgery.  And this introduces the thirdmajor figure of our trio, establishing the germ theory ofdisease, and that's Joseph Lister,who lived from 1827 to 1912, and made his majorcontributions in Scotland. He was professor of surgery atEdinburgh University, where he was appalled by thenumbers of patients who died after otherwise successfuloperations. You know the old joke about theoperation being successful, just too bad the patient died.  Well, Pasteur's ideaimmediately struck him for its lifesaving, practicalimplications. That is, he made practical useof Pasteur's discovery about the role of airborne germs incausing wound infections in surgery.  Now, surgery,before Lister, had a number of major limits.  There was pain itself,and the need for speed. There was blood loss,and there was septicemia. The result was that the majorbody cavities remained off limits: the abdominal cavity,the thoracic cavity, the cranial cavity.  And there was a high rate ofdeath from infection. The idea was thought byphysicians at the time that the infection arose throughspontaneous generation. As tissue died,they gave off toxins that caused infection,and so infection was simply accepted as an inevitable,normal part of surgery. Lister's surgical revolutionoccurred with the work he published,"On the Antiseptic Principle in the Practice ofSurgery," in 1864.  The implications of Pasteur'swork on fermentation were that--you could have an analogy.  If Pasteur was right,there was no spontaneous generation.  An airborne microorganismpenetrated the wound and caused infection or septicemia.  The remedy was to prevent thepenetration of the microorganism,the idea of antisepsis. So, Lister accepted Pasteur'sinsight that infections were not a chemical reaction,caused by oxidation when air touched a wound.  Instead, infection was theresult of contamination, from the outside,of the wound by microorganisms. His solution first was this,the carbolic spray device that he invented.  What you did was to spray theair around the patient, applying carbolic acid alsodirectly to the wound. And Lister also washed hishands before operating, and sterilized his instruments.  There's a stylized idea of aLister-type surgical technique at work.  Well, until Lister'srevolutionary innovation, surgery had been an emergency,a treatment of last resort, because of the wound infection.  After 1866, it became a normalprocedure. There were other innovations aswell, that went with it. His contemporaries improved onLister. You'll see that here theyaren't wearing masks, for example,or gowns. Those are introduced--andgloves made from vulcanized rubber--were introduced in the 1890s, but really became a part ofbest practice only from about the time of the First World War.  This also revolutionalizedobstetrics, with the conquest of puerperalfever, with--hospital and clinicalprocedures then were transformed by the antiseptic idea.  So, by the 1890s,you have the consolidation of the germ theory of disease,revolutionalizing medicine and become accepted throughout theinternational medical profession.  I'd like to mention the impactalso on culture. And this particular book,which is by Bram Stoker, which is Dracula,published in 1897, that gives us,I would argue, expression in a really dramaticand-- I just read it again--a reallyscary-- I assure you--idea of anxietiesabout infection. Now, Dracula is really,for its time, a high-tech novel.  In it you see all about thelatest scientific and medical inventions and ideas.  It contains the phonograph,the telephone, stenography,railroads, the two-wheeled bicycle.  And in medicine it deals withthe latest inventions in psychiatry, in bloodtransfusion, infectious diseases.  And indeed, I would argue,it also involves what was the cutting edge scientific idea inmedicine at the time, the possibility of vector bornediseases like malaria and filarial.  Then it's just at the time whenwe're going to see tropical medicine--we'll look at next time--becomes the cutting edgeof late nineteenth-century, early twentieth-century medicalscience. Now, you know the drill aboutDracula, how Count Dracula--the wordDracula comes from the Romanian word dracul,which means a devil, a little devil.  And you know how he lived,the Count--the evil Count--in Transylvania,in Romania, in the Carpathian Mountains.  And the important point is hetravels by ship from the Black Sea port,aboard a Russian vehicle, through the Mediterranean,and up along the coast of Spain and France,where he lands by ship in Britain at the port of Whitby.  Then he travels by train,and is transported by railroad from Whitby to London,where his plan is to ravage the huge population of London.  Now, what does that remind youof? Doesn't that--it remindsme--I'm going to argue that Dracula is many things.  In literature,you'll see that Dracula is a metaphor--and this is oftensaid--for repressed sexuality, in the Victorian Era.  You'll find interpretations ofit as expressing also a repressed homoeroticism.  In it, we also find expressionof the battle of good and evil. That's our friend Dracula.  And you'll see--love neverdies--the idea of--the sexual idea is clearly--some 200 filmshave been made of Dracula.  And you can see clearlypossible sexual ideas in films such as this.  And they're clearly also here.  But what I want to argue iswhat's been neglected so often-- and I think it's reallyimportant--is I want to argue that Dracula is also anallegory of infectious disease; not a specific disease,but diseases like plague and cholera,that originated in Eastern Europe and traveled,just as Dracula did, by ship and by railroad;that they had Count Dracula's goal of ravaging industrialcities, huge population centers like London.  And it's interesting that thevampire hunters in the novel are doctors, physicians,whose mission is to destroy the invading vampire.  Also involved,we see, is the seasonality. It's not by chance that CountDracula arrives in late August/September,just as cholera would have, or bubonic plague.  And we see miasmatism in thenovel: the flowers, the garlic, the mistssurrounding Dracula. And I would argue that Draculais a composite of many infections.  Here's the handsome count again.  And I'd like to show you onemore handsome picture of him; and that's that one.  And I would argue that thisclearly makes me think also of vector-borne disease,and possibly this is a million miles removed from malaria andfilarial, which we'll be talking aboutnext week. So, I urge you also to readDracula. I'm sure you'll enjoy it asmuch as I did.