HISTORY OF ZOOLOGY 



47 



Louis Pasteur (1822-1895) was a French scientist who had been 

 trained in chemistry but became one of the outstanding pioneers 

 in applied biology and medicine. In 1861 he put an end to the 

 controversy regarding spontaneous generation of living organisms 

 and established the idea that all life in present times comes from 

 preexisting life. He showed that living organisms cause fermenta- 

 tion and demonstrated that these organisms and others could be 

 killed by heating them to a certain temperature. He showed that 

 materials thus heated and then sealed would not ferment until after 

 they were exposed to the organisms in the air. The pasteurization 



Fig. 16.— Louis Pasteur (1822-1895), one of the benefactors of mankind. (From 

 Garrison, History of Medicine, published by W. B. Saunders Company.) 



process grew out of these experiments. He rescued the silk in- 

 dustry of southern Europe by discovering the organism which killed 

 the insects, and he also discovered an immunization process and 

 treatment for hydrophobia. 



Thomas Henry Huxley (1825-1895) Avas one of the most popular 

 English scientists of his day. He was one of the principal champions 

 of Darwin's ideas and theories. Comparative anatomy and paleon- 

 tology were greatly advanced through his influence. 



August Weismann (1834-1914) was a German zoologist who started 

 out as a physician after having been trained in that field. He was 



