20 BACTERIOLOGY 



almost to a germ-mania. It became the fashion to suspect 

 the presence of these organisms in all forms and kinds of 

 disease, simply because they had been demonstrated in 

 the mouth, intestinal evacuations, and water. 



Though nothing of value at the time had been done in 

 the way of classification, and even less in separating and 

 identifying the members of this large group, still the fore- 

 most men of the day did not hesitate to ascribe to them not 

 only the property of producing pathological conditions, 

 but some even went so far as to hold that variations in the 

 symptoms of disease were the result of differences in the 

 behavior of the micro-organisms in the tissues. 



Marcus Antonius Plenciz, a physician of Vienna in 1762, 

 declared himself a firm believer in the work of Leeuwenhoek, 

 and based the doctrine which he taught upon the discoveries 

 of the Dutch observer and upon observations of a confirma- 

 tory nature which he himself had made. The doctrine of 

 Plenciz assumed a causal relation between the micro-organ- 

 isms discovered and described by Leeuwenhoek -and all 

 infectious diseases. He maintained that the material of 

 infection could be nothing else than a living substance, 

 and endeavored on these grounds to explain the variations 

 in the period of incubation of the different infectious diseases. 

 He likewise believed the living contagium to be capable of 

 multiplication within the body, and spoke of the possibility 

 of its transmission through the air. He believed in the 

 existence of a special germ for each disease, holding that 

 just as from a given cereal only one kind of grain can grow, 

 so by the special germ for each disease only that disease 

 can be produced. 



He found in all decomposing matters innumerable minute 



animalculae," and was so firmly convinced of their etio- 



