44 2 BACTERIOLOGY. 



Leeuwenhoek's successors busied themselves 

 with describing and classifying these u infu- 

 sion animals." Among these investigators are 

 especially to be mentioned v. Gleichen-Russ- 

 worm (1778) and Otto Friedrich Miiller 

 (1786), the latter of whom made good drawings, 

 applied many of the names we still use and 

 established genera still recognized. Bory de 

 St. Vincent (1824) made a further advance, 

 and in 1838, Ehrenberg, and in 1841, Dujardin' 

 followed with new discoveries, which were 

 added to in 1852 by Pert/y and in 1853 by Ferdi- 

 nand Colin. In opposition to their predeces- 

 sors these later investigators reckoned bacteria 

 among the true plants and Perty clinched the 

 demonstration by the discovery of endogenous 

 spore-formation. 



Cohn sought to develop the systematic 

 classification of bacteria. He carried out a 

 system of separation into many genera and 

 species, laying stress upon the differences ob- 

 served. Perty recognized clearly the occur- 

 rence of a variation in form according to the 

 substratum, whereas before this there had been 

 simply a general recognition of a Protean-like 

 change of form. 



From the time of Kirch er onward, the doc- 

 trine of a " contagium animatum" went hand 

 in hand with the amassing of this systematic 



