THE CAUSATION OF DISEASE. 36 1 



change from the homogeneous to the heterogeneous, and the 

 several members become more and more unlike one another ; 

 but, under the stimulus of bacterial irritation, there is disso- 

 lution, and the affected tissues revert to ground common to 

 the whole class. 



Wherefore I am led, on a priori grounds, to conclude that 

 malignant disease is due to peculiarity of both S and E — pecu- 

 liarity of S, as already set forth, and peculiarity of E in the 

 shape of a specific parasite. 



