24 HISTORICAL INTRODUCTION 



Fracastorius, his theory of a "hving cause" for various dis- 

 eases was pubHshed in 1671, but received httle support. 



The discoveries of Leeuwenhoek which proved the exist- 

 ence of microscopic organisms soon revived the "contagium 

 vivum" idea of Kircher. Nicolas Andry in a work pub- 

 hshed in 1701 held such views. Lancisl in 1718 advanced 

 the idea that "animalcules" were responsible for malaria, a 

 view not proved until Laveran discovered the malarial para- 

 site in 1880.1 Physicians ascribed the plague which visited 

 Southern France in 1721 to the same cause, and many even 

 went so far as to attribute all disease to animalcules, which 

 brought the theory into ridicule. Nevertheless, the "con- 

 tagium vivum" theory survived, and even Linnaeus in his 

 Systema Naturae (1753-6) recognized it by placing the 

 organisms of Leeuwenhoek, the contagia of diseases and the 

 causes of putrefaction and fermentation in one class callfed 

 "Chaos." 



Plenciz, a prominent physician and professor in the Vienna 

 Medical School, published in 1762 a work in which he gave 

 strong arguments for the "living cause" theory for trans- 

 missable diseases. He taught that the agent is evidently 

 transmitted through the air and that there is a certain 

 period of incubation pointing to a multiplication within the 

 body. He also believed that there was a specific agent 

 for each disease. His writings attracted little attention at 

 the time and the "contagium vivum" theory seems to have 

 been almost lost sight of for more than fifty years. Indeed, 

 Oznam, in 1820, said it was no use to waste time in refuting 

 hypotheses as to the animal nature of contagium. 



Isolated observers were, however, keeping the idea alive, 

 each in his own locality. In 1787 Wollstein, of Vienna, 

 showed that the pus from horses with glanders could infect 

 other horses if inoculated into the skin. Abilgaard, of 

 Copenhagen, made similar experiments at about the same 

 time. In 1797 Eric Viborg, a pupil of Abilgaard's, published 

 experiments in which he showed the infectious nature not 



1 Sir H. A. Blake ha3 called attention to the fact that the "mosquito 

 theory" of malaria is mentioned in a Sanscrit manuscript of about the 6th 

 century A.D. 



