24 Introduction 



that the definite relationship between bacteria and disease 

 has been determined. 



Briefly summarized, these requirements are as follows: 



1. A specific micro-organism must be constantly asso- 

 ciated with the disease. 



2. It must be isolated and studied apart from the disease. 



3. When introduced into healthy animals it must pro- 

 duce the disease, and in the animal in which the disease 

 has been experimentally produced the organism must be 

 found under the original conditions. 



In 1849 J. K. Mitchell, in a brief work upon the "Crypto- 

 gamous Origin of Malarious and Epidemic Fevers," fore- 

 shadowed the germ theory of disease by collecting a large 

 amount of evidence to show that malarial fevers were due 

 to infection by fungi. 



Pollender (1849) and Davaine (1850) succeeded in 

 demonstrating the presence of the anthrax bacillus in 

 the blood of animals suffering from and dead of that dis- 

 ease. Several years later (1863) Davaine, having made 

 numerous inoculation experiments, demonstrated that this 

 bacillus was the materies morbi of the disease. The bacillus 

 of anthrax was probably the first bacterium shown to be 

 specific for a disease. Being a very large bacillus and a 

 strongly vegetative organism, its growth was easily observed, 

 while the disease was one readily communicated to animals. 



In 1873 Obermeier observed that actively motile, flexible 

 spiral organisms were present in large numbers in the 

 blood of patients in the febrile stages of relapsing fever. 



Klebs, who was one of the pioneers of the germ theory, 

 published, in 1872, a work upon septicemia and pyemia, 

 in which he expressed himself convinced that the causes 

 of these diseases must come from without the body. Bill- 

 roth, however, strongly opposed such an idea, asserting 

 that fungi had no especial importance either in the processes 

 of disease or in those of decomposition, but that, existing 

 everywhere in the air, they rapidly developed in the body 

 as soon as through putrefaction a "Faulnisszymoid" (putre- 

 factive ferment), or through inflammation a "Phlogisti- 

 schezymoid" (inflammatory ferment), supplying the neces- 

 sary feeding-grounds, was produced. 



In 1875 the number of scientific men who had entirely 

 abandoned the doctrine of spontaneous generation and 

 embraced the germ theory of disease was small, and most 

 of those who accepted it were experimenters. A great 



