430 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



or could have gone on just the same by mere selection 

 and adventitious variation." 



c. Inheritance of Characters Due to Disease. 



Under this head Brewer cites a well-known case. 

 He says : "The most extensive and complete set of 

 experiments yet published on the artificial production 

 of disease by mechanical injuries are those of Dr. 

 Brown-Sequard on the artificial production of epilepsy. 

 This is a disease which is certainly sometimes heredi- 

 tary and which may also be produced by a^ t in previ- 

 ously sound animals. He experimented with guinea 

 pigs and produced many artificial epileptics, and by 

 breeding these he produced many congenital epilep- 

 tics. The disease artificially produced in the parents 

 was transmitted to the offspring in numerous cases. 

 The acquired characters in those cases were certainly 

 transmitted to the offspring and became hereditary. 

 These experiments were continued and repeated by 

 his assistant and pupil Depuy, and the results abund- 

 antly confirmed. It was shown, moreover, that in 

 many cases it was the tendency to become epileptic that 

 was transmitted rather than the disease itself. Just 

 as in a great majority of cases of strictly hereditary 

 disease it is the constitutional tendency rather than 

 the disease itself that is commonly transmitted, 



"These experiments have now been before the 

 world some years, during which time ideas have greatly 

 changed as to the causes of disease, and the nature of 

 hereditary tendencies, but as yet there are no pub- 

 lished accounts of experiments indicating that those of 

 Brown-Sequard and of Depuy were not carefully per- 

 formed, or that the conclusions were illusive. Medical 

 literature abounds with alleged instances where ner- 



