388 



GERM THEORY AND SPONTANEOUS GENERATION. 



by discovering a preventive bestowed an in- 

 calculable benefit upon his own country and 

 upon the world. Pasteur even succeeded in 

 excluding the germs from an infusion by stop- 

 ping the flask with a tight plug of cotton wool, 

 and, on examination with the microscope, 

 found the germs adhering to the cotton. His 

 strongest proof of the diffusion of the germs of 

 bacteria in the atmosphere was furnished by 

 his famous experiment, many times successful- 

 ly repeated, with flasks with bent necks, the 

 mouth opening downward. Sterilized organic 

 substances have maintained their original fresh- 

 ness in such uncorked vessels through a series 

 of a dozen years. 



Pasteur's germ theory, supported by such 

 searching tests, was accepted by pathologists 

 as a probable explanation of contagious and 

 epidemic diseases. The parasitic theory of ma- 

 laria and contagion was prepared for by the 

 revelation of numerous new entozoic parasites 

 by the microscope ; while the doctrine of spon- 

 taneous generation had lost some of its strong- 

 est evidence through the discovery of the iden- 

 tity of the tapeworm with the Cysticercus, of 

 the sexual process of the Trichina, and of the 

 manner of the introduction of these parasites 

 into the animal system. The uniformity of the 

 symptoms in epidemic and infectious diseases, 

 so strongly analogous to the reproduction of 

 species, and the certainty that the seeds of 

 epidemics are transmitted through the air, and 

 in clothing and such articles as might harbor 

 microscopic organic germs, led scientific men, 

 after the discovery by Pasteur of the fact that 

 the embryos of the organic agents in fermen- 

 tation and putrefaction are conveyed through 

 the atmosphere, to associate the analogous de- 

 generation of the tissues and fluids of the body 

 in contagious diseases with the idea of similar 

 organic germs. The process of putrefaction, 

 or something very similar, was seen to occur 

 and spread in the living body after mechanical 

 local injuries, and it was a natural inference 

 that the bacteria of putrefaction were also 

 here at work. Tyndall confirmed this hypo- 

 thesis by his examination of the air of a 

 room in which he had removed the bandage 

 from a partially healed wound, which after- 

 ward grew rapidly worse, and was followed 

 by an abscess. A few years later, in 1876, he 

 opened several flasks in the same room, and 

 found the air strongly impregnated with the 

 germs of putrefactive bacteria. 



The germ theory of disease was greatly 

 strengthened by the discovery of the connec- 

 tion of a bacterium (Bacillus anthroKi*), visible 

 under the microscope, with the deadly epi- 

 demic which attacks animals, and sometimes 

 human beings, in certain parts of Europe, and 

 which is called splenic fever. Recent investi- 

 gations have shown that the fatal agent in this 

 disease is the spores rather than the developed 

 bacterium. Inoculating mice with dried dis- 

 eased blood in which there were no spores 

 visible, Dr. Koch, a German physician, found 



that the power of infection was not preserved 

 longer than five weeks. Experimenting with 

 dried blood in which the spores had separated, 

 he found it as virulent in its action after four 

 years as the fresh blood of a diseased animal. 

 Koch, and afterward Cohn and Pasteur, ob- 

 served under the microscope the propagation 

 of this animalcule. Its appearance and be- 

 havior are like those of the hay bacterium 

 (Bacillus subtilis). Infecting a drop of the 

 aqueous humor of an ox's eye with a speck of 

 diseased blood, and warming the microscope, 

 Koch saw the short rods begin to lengthen; 

 in three or four hours they were ten to twenty 

 times, and in a few more hours a hundred 

 times their original length ; in some cases they 

 ran out parallel to each other, and in others 

 they were beautifully curved, intricately inter- 

 laced, or matted together. He finally observed 

 the spores forming within the filaments along 

 their whole length, and saw the integument 

 after a while fall to pieces, releasing the minute 

 ovoid seeds, which his later experiments proved 

 to be the infectious principle. The joint ob- 

 servations of Pasteur and Joubert on splenic 

 fever enabled them to clear up much which 

 was confused and obscure regarding its pathol- 

 ogy, by discovering that it was often compli- 

 cated with septicaemia, whose symptoms were 

 taken for its own. The theory of contagium 

 vivum in miasmatic and infectious disease has 

 lately become the prevalent one in the medical 

 profession, especially since the discovery of 

 the presence of bacteria in the diseased humors 

 of patients affected with diphtheria. The germ 

 theory of Pasteur, applied to the mortification 

 of wounds and abscesses, was the basis of Pro- 

 fessor Lister's antiseptic treatment in surgery 

 with carbolic <acid, which has already shown 

 itself an incalculable advance- in hospital prac- 

 tice. 



Tyndall's attention was attracted to the germ 

 theory by noticing the coincidence that he could 

 best cleanse the air of floating particles, in or- 

 der to conduct his observations on the progress 

 of heat-waves, by the same processes which 

 Pasteur and Lister used to destroy the germs 

 of bacteria. In examining air long kept still, 

 air filtered through cotton wool, calcined air, 

 and air filtered by breathing, by the light of a 

 beam brought to a focus in a dark place, he 

 found that in every case the air which they 

 found inefficient to produce fermentation in 

 sterilized infusions was that which was free 

 from floating corpuscles. From this he in- 

 ferred the identity of the floating motes of the 

 air with the germs which produce fermentation, 

 putrefaction, and disease. He presented the 

 results of his observations and reflections be- 

 fore the Royal Society, and in the " Times 's 

 newspaper in the beginning of the year 1870, 

 and was immediately confronted by Dr. Bas- 

 tian. The dust in the air which is seen in the 

 sunbeam Tyndall assumes to be composed of 

 organic particles. He found by experiment 

 that it can be burned. He noticed the curious 



