INTRODUCTION. 25 



cules exhibited by the microscope and the origin of dis- 

 ease, and advanced this opinion as early as 1762. Un- 

 fortunately, the opinions of Plencig seem not to have 

 been accepted by others, and were soon forgotten. 



In 1704 John Colboch described "a new and secret 

 method of treating wounds by which healing took place 

 quickly, without inflammation or suppuration." 



Boehm succeeded in 1838 in demonstrating the occur- 

 rence of yeast plants in the stools of cholera, and con- 

 jectured that the process of fermentation was concerned 

 in the causation of that disease. 



In 1840 Henle, considering all the evidence that had 

 been collected, determined that the cause of the infec- 

 tious diseases was to be sought for in minute living 

 organisms or fungi. He may be looked upon as the real 

 propounder of the Germ Theory of Disease, for he 

 not only collected facts and expressed opinions, but also 

 investigated the subject ably. The requirements which he 

 formulated in order that the theory might be proved were 

 so severe that he was never able to attain to them with 

 the crude methods at his disposal. They were so ably 

 elaborated, however, that in after years they were again 

 postulated by Koch, and it is only by strict conformity 

 with them 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. 



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 



