THE HISTORY OF BACTERIOLOGY. 65 



and although parasites had long been accepted as the cause 

 of certain diseases in plants, this was really the first fully- 

 described and well-authenticated instance of a fungus para- 

 site giving rise to disease in any members of the animal 

 kingdom. 



As the direct outcome of these researches, Henle, in 1840, 

 was led to believe that the cause of miasmatic, infective and 

 contagious diseases must be looked for in living fungi or 

 other minute living organisms, and although he was unable, 

 experimentally, to satisfy himself of the accuracy of his 

 position, he was fully convinced that he was working in the 

 right direction. It would indeed have been difficult, at that 

 period, to satisfy every condition that he required to be 

 fulfilled ; the methods now in use were then unknown 

 and have only been perfected by workers as it has been 

 found necessary, from time to time, to comply in the most 

 minute detail with Henle's conditions, and as, one point 

 being carried, it has been found necessary to advance on 

 others. The first of these was that a specific organism should 

 always be associated with the disease under consideration. 

 As such presence, however, might be accidental, these 

 organisms were to be found not only in pus but actually in 

 the living body. As they might be, even then, merely 

 parasitic, and not associated directly with the causation of 

 the disease, it would be necessary to isolate the germs, the 

 contagium organisms and the contagium fluids, and to 

 experiment with these separately with special reference to 

 their power of producing similar disease in other animals. 

 We now know that it has only been by strict compliance 

 with all these conditions, again postulated by Koch, that the 

 most brilliant scientific observers and experimentalists in 

 England, France, and Germany have been able to determine 

 the causal connection between micro-organisms and disease. 

 After Henle's work appeared a regular fungus fever set in ; 

 many skin diseases were proved to be the result of the 

 action of fungi, and numerous internal diseases were, on 

 very imperfect evidence, said to be due to parasitic agency ; 

 and a large number of diseases which we now consider to be 

 caused by the action of certain specific organisms in the 

 system, were deemed, on very imperfect data however, to 

 be due to these fungi. Cholera and typhoid fever became 

 subjects of great interest, the stools from patients suffering 



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