CANCER. 183 



from such causes get cancer are predisposed to it 

 constitutionally. On this point Professor von Esmarch 

 says : " One has always to come back to the assump- 

 tion that a certain predisposition is a necessary factor. 

 Without this it is impossible to explain how it is that, 

 in the great majority of cases in which irritation exists, 

 cancer does not become developed." 



Without this hereditary predisposition not even 

 inoculation will convey the disease. Alibert and other 

 investigators inoculated themselves with cancerous 

 matter, and Harley and Lawrence performed the same 

 operation upon dogs, without effect ; which clearly 

 shows that if there be no predisposition, if the soil 

 be not by nature suitable, even the introduction of 

 the bacillus if there be a bacillus or of the poison 

 into the system will fail to establish the disease. Just 

 as some are born with a predisposition to consumption, 

 and fall victims to the disease under conditions harm- 

 less to those not so predisposed, so others are born 

 with a predisposition to cancer, and in these the malig- 

 nant disease lights up from injury or irritation, which 

 the healthy undergo with impunity. 



On the ground, then, that predisposition accounts 

 for the appearance of cancer in the individual, the 

 alarming increase of the disease among the population 

 is to be attributed to propagation and cultivation of 

 this predisposition. In the spread of this family pre- 

 disposition there are two agencies at work. First, 

 and by far the most powerful, is hereditary transmis- 

 sion; for just as epilepsy, suicide, and drunkenness are 



