A HISTORY OF SCIENCE 



was excluded altogether from France; and the whole 

 subject thus came prominently to public attention. 

 But important as the trichina parasite proved on its 

 own account in the end, its greatest importance, after 

 all, was in the share it played in directing attention at 

 the time of its discovery in 1833 to the subject of mi- 

 croscopic parasites in general. 



The decade that followed that discovery was a time 

 of great activity in the study of microscopic organisms 

 and microscopic tissues, and such men as Ehrenberg 

 and Henle and Bory Saint-Vincent and Kolliker and 

 Rokitansky and Remak and Dujardin were widening 

 the bounds of knowledge of this new subject with de- 

 tails that cannot be more than referred to here. But 

 the crowning achievement of the period in this direc- 

 tion was the discovery made by the German, J. L. 

 Schoenlein, in 1839, that a very common and most dis- 

 tressing disease of the scalp, known as favus, is really 

 due to the presence and growth on the scalp of a vege- 

 table organism of microscopic size. Thus it was made 

 clear that not merely animal but also vegetable organ- 

 isms of obscure, microscopic species have causal rela- 

 tions to the diseases with which mankind is afflicted. 

 This knowledge of the parasites was another long step 

 in the direction of scientific medical knowledge; but 

 the heights to which this knowledge led were not to be 

 scaled, or even recognized, until another generation of 

 workers had entered the field. 



PAINLESS SURGERY 



Meantime, in quite another field of medicine, events 

 were developing which led presently to a revelation of 



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