20 BACTERIOLOGY. 
Perty, in 1852, drew attention to the vegetable 
origin of these minute organisms ; Robin, in 1853, 
suggested their relationship to the alge ; Davaine, in 
1859, emphasized this fact ; and since it has been con- 
firmed by the investigations of Cohn, Niageli, and 
others. Bacteria are now generally believed by bacte- 
riologists to be vegetable organisms, schizomycetes, or 
fission-fungi, closely allied to the alge. 
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 Kircher and Leeuwenhoek, and the ‘ animalcule ” 
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 Linné, 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- 
