( 2*1 ) 241 



important result, that when a decoction of meat is effect- 

 ually screened from ordinary air, and supplied solely 

 with air which has been raised to a high temperature, 

 putrefaction never sets in. Putrefaction, therefore, he 

 affirmed to be caused by something derived from the air, 

 which something could be destroyed by a sufficiently 

 high temperature. The experiments of Schwann were 

 repeated and confirmed by Helmholtz and Ure. But 

 as regards fermentation, the minds of chemists, influ- 

 enced probably by the great authority of Gay-Lussac, 

 who ascribed putrefaction to the action of oxygen, fell 

 back upon the old notion of matter in a state of decay. 

 It was not the living yeast plant, but the dead or dying 

 parts of it, which, assailed by oxygen, produced the fer- 

 mentation. This notion was finally exploded by Pasteur. 

 He proved that the so-called " ferments" are not such ; 

 that the true ferments are organized beings which find 

 in the reputed ferments their necessary food. 



Side by side with these researches and discoveries, and 

 fortified by them and others, has run the germ theory of 

 epidemic disease. The notion was expressed by Kircher, 

 and favored by Linnaeus, that epidemic diseases are due 

 to germs which float in the atmosphere, enter the body, 

 and produce disturbance by the development within the 

 body of parasitic life. While it was still struggling 

 against great odds, this theory found an expounder and 

 a defender in the President of this Institution. At a 

 time when most of his medical brethren considered 

 it a wild dream, Sir Henry Holland contended that 

 some form of the germ theory was probably true. The 

 strength of this theory consists in the perfect parallelism 

 of the phenomena of contagious disease with those of 

 life. As a planted acorn gives birth to an oak compe- 



