MICRO-ORGANISMS AS EXCITING AGENTS OF DISEASE. 91 



of the disease, and the subsequent immunity, pointed 

 more or less distinctly to the organised nature of the 

 causal agents, and could be explained by the mode of 

 development of these supposititious beings. The anxiety 

 to find a relation between the phenomena of infective 

 diseases and those of fermentation and putrefaction, is 

 shown by the fact that by some pathologists the whole 

 group of infective diseases was designated by the term 

 " Zymotic diseases." 



These views, which have continuously gained ground 

 during the last forty years, did not, it is true, at first 

 rest on clear knowledge, and were wanting in an experi- 

 mental basis. They were only based on speculations ; 

 but these speculations were made with such acuteness, 

 and with such logic, that they led to almost the same 

 results as were arrived at forty years later by elaborate 

 experimental investigations. It was more especially Henie's 



TT , , . ,. * n m -i T 7 T T deductions. 



Henle who, in the year 1840, in his Pathologischen 

 Untersuchungen, and later, in 1853, in his Handbuck 

 der rationellen Pathologie, sketched with wonderful pre- 

 cision the relation of micro-organisms to the infective 

 diseases, and defined the intimate nature, the vital pro- 

 perties, and the mode of action of the micro-organisms, 

 as well as the dependence of the individual phases and 

 symptoms of the diseases in question on the behaviour of 

 the parasites, almost as accurately as has subsequently 

 been done as the result of direct observations with optical 

 aids, at that time unknown, and of numerous experiments. 

 The great influence which Henie's views have exercised 

 on the further development of knowledge on the subject 

 of the parasitic exciting agents of disease renders it 

 necessary for us to reproduce at this place some of the 

 most important of these views in his own words : 



" If we trace the miasmatic contagia in their action on the 

 animal organism, we find at once, although with many in- 

 dividual differences, a general and characteristic property 

 which can only be ascribed to living matter, namely, that of 

 multiplying at the cost and by the assimilation of foreign 

 organic material. This conclusion is supported by the course 

 of the great majority of miasmatic contagious diseases. They 



