THE BEGINNINGS OF LIFE. 361 



invariable fatality of the general parasitic disease is 

 precisely what might have been anticipated. 



It would, therefore, follow from these views, (i) that 

 the development of the parasites in the latter affec- 

 tions is altogether secondary, in order of time, to the 

 blood-changes by which they are produced; and, as I 

 have already hinted, it would seem to indicate (2) that 

 even in cases of the spread of such diseases by con- 

 tagion, the contagious element, whether living or not 

 living, operates by its power of initiating certain mole- 

 cular changes — which, gradually extending throughout 

 the body, may or may not in their turn cause the 

 evolution of new organisms. That is to say, we have, 

 at first, always to do with a mere contact-action, and 

 even in the case of general parasitic diseases, the direct 

 multiplication of the infecting agent itself is only an 

 unimportant accessory process as compared with the 

 spreading changes initiated by its contact-action. 



Already-existing evidence is thoroughly harmonious 

 with such views. 



In the first place, it is admitted even by those who 

 are pure contagionists, that a blood-change is the 

 primary and necessary initiator of one of these diseases. 

 Thus, M. Robin says : — ' Les circonstances qui parais- 

 sent favorable au developpement de la Muscardine sont 

 celles qui ont pour premier resultat une alteration des 

 humeurs ou des organes de I'animal vivant, et c'est a la 

 suite de certe alteration que le parasite se developpe. . . 

 Le developpement du Botrytls est done bien plutot con- 



