20 BACTERIOLOGY. 



Perty, in 1852, drew attention to the vegetable 

 origin of these minute organisms ; Robin, in 1853, 

 suggested their relationship to the algae ; Davaine, in 

 1859, emphasized this fact ; and since it has been con- 

 firmed by the investigations of Cohn, Nageli, and 

 others. Bacteria are now generally believed by bacte- 

 riologists to be vegetable organisms, schizomycetes, or 

 fission-fungi, closely allied to the algse. 



From the earliest investigations into the life-history 

 and properties of bacteria these micro-organisms have 

 been thought to play an important part in the causa- 

 tion of infectious diseases. The doctrine of contagium 

 aminatum was based upon the discoveries of Athana- 

 sius Kircherand Leeuwenhoek, and the " animalculse " 

 then observed in organic materials were believed to be 

 the cause of the great epidemics of the day, such as 

 the plague. Shortly after these first investigations, 

 Lange and Hauptmann advanced the opinion that 

 puerperal fever, measles, smallpox, typhus, pleurisy, 

 epilepsy, gout and many other diseases were due to 

 animal contagion. Andry and Linne, in 1701, as- 

 sumed the same cause for syphilis, and Lancisi, in 

 1718, for malaria. In fact, so wide- spread became the 

 belief in a causal relation of these minute organisms to 

 disease that it soon amounted to a veritable craze, and 

 all forms and kinds of diseases were said to be pro- 

 duced in this way, upon no other foundation than that 

 these organisms had been found in the mouth and in- 

 testinal contents of men and animals, and in water. 



Among those who were especially conspicuous at 

 this time for their advanced views on the germ-theory 

 of infectious diseases was Marcus Antonius Plenciz, a 

 physician of Vienna. This acute observer, who pub- 



