40 



may be chosen and the organic product, whether 

 milk or any other article, remains without under- 

 going change. 



The step from the action exerted by bacteria 

 as agents exciting the decomposition of organic 

 products to that which brings them before us as a 

 source of disease is not a great one. In the one 

 case they lead to change which would not otherwise 

 occur, and in the other they disturb the order of 

 changes naturally taking place and thus induce an 

 abnormal state ; and although there is nothing in 

 their morphological characters to show the reason, 

 different trains of phenomena — in other words 

 different diseases — are occasioned by different 

 kinds of bacilli. 



It is in the group of disorders falling under the 

 denomination of contagious or infectious febrile 

 diseases, a form of disease taken in its entirety 

 constituting one of the greatest scourges besetting 

 the human race, that we are brought most manifestly 

 into contact with bacilli. Very diverse views have 

 been held at different times regarding the nature 

 and mode of production of the affections belonging 



