28 mSfomCAL INTRODUCTION 



teria which produce disease in men and animals were iso- 

 lated and described. It is well to remember that the first 

 specific disease of man proved to be caused by a hnrtcriuvi 

 was tuberculosis, by Koch in ]S<S2. 



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 technie and solid cultures for 

 isolation and study, 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 trypanosomiases 

 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 dis- 

 covery of diphtheria antitoxin by Behring, and independently 

 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 bactei-ia 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 very 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 dis- 

 cussion on spontaneous generation and the "contagium 

 vivum" theory which followed Leeuwenhoek's discoveries. 

 Plenciz (1762) appears to have first formulated this belief 



