310 BRIEF HISTORY OF BACTERIOLOGY UP TO 1881 



Progress was greatly assisted by the introduction of anilin 

 dyes as suitable stains for organisms by Weigert in 1877, by 

 Koch's application of special technic and gelatin cultures 

 for isolation and study, 1881, and the great improvements 

 in the microscope by Prof. Abbe, of Jena. 



Laveran's discovery of the malarial parasite in 1880 

 turned attention to protozoa as the causes of disease and led 

 to the discovery of the various piroplasmoses and trypano- 

 somiases in man and the lower animals. 



Pasteur's protective inoculations in chicken cholera and 

 anthrax directed attention to the possibility of using bac- 

 teria or their products as a specific protective or curative 

 means against particular diseases. This finally led to the 

 discovery of diphtheria antitoxin by Behring, and indepen- 

 dently by Roux, in 1890, a discovery which opened up the 

 wide field of immunity which is so persistently cultivated at 

 the present time. 



While the causation of disease by bacteria has probably 

 attracted most attention, especially in the popular mind, it 

 should not be forgotten that this is but one of the numerous 

 ways in which these organisms manifest their activities, and 

 in a sense it is one of their least-important ways, since other 

 kinds are essential in many industries (dairying, agriculture) 

 and processes (sewage purification), and are even indispen- 

 sable for the wry existence of all green plants and hence of 

 animals, including man himself. 



PUTREFACTION AND FERMENTATION. 



The idea that there is a certain resemblance between 

 some infectious diseases and the processes of putrefaction 

 and fermentation seems to have originated during the 

 discussion on spontaneous generation and the "contagium 

 vivum" theory which followed Leeuwenhoek's discoveries. 

 Plenciz (1762) appears to have first formulated this belief 

 in writing. He considered putrefaction to be due to the 

 ''animalcules," and said that it occurred only when there 

 was a coat of organisms on the material and only when 

 they increased and multiplied. Spallanzani's experiments 



