Page:The Harveian oration (electronic resource) - delivered at the Royal College of Physicians, October 18th, 1886 (IA b2041190x).pdf/44

 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 discase 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