4 MICROBIOLOGY 



the experiments made by such workers as Dujardin to 

 advance to a successful conclusion. 



Until about 1850, the appearance of these organisms, 

 animalcula as they were then called, in liquids such as meat 

 broth was considered as a mere chance phenomenon. At 

 the same time very appreciable changes were observed in 

 the liquid in question, but no one supposed that there existed 

 between the two orders of facts such a close relation as 

 cause and effect. 



To Pasteur belongs the great honor of having estab- 

 lished beyond a doubt the close connection or causal rela- 

 tion between fermentative changes in certain liquids and 

 the development within them of bacteria. In his work on 

 fermentation of milk he laid the foundation for the physio- 

 logical study of microorganisms. 7 What he had shown by 

 this fermentation he applied to others and made a succes- 

 sion of scientific studies and experiments the results of 

 which have perhaps never been surpassed. 



Pasteur introduced the physiology of bacteria, and 

 Davaine pointed to the significance of their pathological 

 powers. Pasteur's studies on the disease of the silk worm 

 were the first to be made on the cause of an infectious dis- 

 ease, although Pollancfer, Davaine and others had observed 

 rod-shaped bodies in the blood of animals dead of anthrax. 



It was not, however, until about 1870 that the subject 

 was taken up by pathologists, who from that time to this 

 have contributed more than any others to the upbuilding of 

 the science of bacteriology. With the publication of Robert 

 Koch's first studies on anthrax began the activity of numer- 

 ous investigators, whose incessant industry has furthered 

 our knowledge of these minute organisms and has accumu- 

 lated a vast literature. Before this period of expansion and 

 rapid growth, bacteria had been studied chiefly by botan- 

 ists of whom Cohn and Nageli were most active. Their work 



T Pasteur. Memoire sur la fermentation appelee lactique (Ann. 

 de chim. et de phys., 2e serie, LII, p. 404). 



