HISTORICAL SKETCH 21 



that the temperature of boiling water was not sufficient to destroy all 

 living organisms, and that, especially in alkaline liquids, a higher 

 temperature was required to ensure sterilization. He showed that at 

 a temperature of 110 to 112 ('., however, which he obtained by boiling 

 under a pressure of one and one-halt' atmospheres, all living organisms 

 were invariably killed. 



Pasteur at a later date (1865) demonstrated that the organisms which 

 resist the boiling temperature are, in fact, reproductive bodies, which 

 are now known as .vywr.v. 



In lN7i> the development of spores was carefully investigated and 

 explained by Ferdinand Colin. He, and a little later Koch, showed 

 that certain rod-shaped organisms possess the power of passing into 

 a resting or spore stage under peculiar conditions of growth, and when 

 in this stage they are much less susceptible to the injurious action of 

 higher temperatures than when in their normal vegetative condition. 



With this discovery the controversy of spontaneous generation, in so 

 far as it related to identified bacteria, was finally settled. If these micro- 

 organisms, some of them being capable of producing the more resistant 

 spores, were present in the air, dust, soil, water, etc., it was easy enough 

 to explain the irregularities in the previous experiments; nor was it any 

 longer to be doubted that these bacteria, through their products, were 

 the cause, not the effect, of fermentation and putrefaction, and that 

 when organic substances were completely sterilized and protected against 

 the entrance of living germs from \vithout, no development of micro- 

 organisms occurred in them. 



Stimulated by the establishment of the fact, through Pasteur's investi- 

 gations, that fermentation and putrefaction were due to the action of 

 living organisms reproduced from similar pre-existing forms, and that 

 each form of fermentation was due to a special micro-organism, the 

 study of the causal relation of micro-organisms to disease was taken 

 up with renewed vigor. Reference has already been made to the 

 opinions and hypotheses of the earlier observers as to the microbic 

 origin of infectious diseases. The first positive grounds, however, for 

 this doctrine, founded upon actual experiment, were the investigations 

 into the cause of certain infections diseases in insects and plants. Thus, 

 Bassi in 1837 demonstrated that a fatal infectious malady of the 

 silkworm muscardine was due to a parasitic micro-organism. Pasteur 

 later devoted several years' study to an exhaustive investigation into 

 the same subject; and in like manner Tulasse in 1864 and Kiihne 

 in 1855 showed that certain specific affections in grains, the potato, 

 etc., were due to the invasion of parasites. 



Very soon after this it was demonstrated that micro-organisms were 

 probably the cause of certain infectious diseases in man and the higher 

 animals. Bacteriological research has always been of special interest 

 to physicians. Many of the most distinguished physicians of the day, 

 in the earlier history of the science, concerned themselves in these 

 investigations, and the progress made during the past fifteen or twenty 

 years has been largely due to their work. Davaine, a famous French 



