70 DARWINISM AND RACE PROGRESS. 



hereditary defects in the nervous system associated 

 with incapacity, a tendency to insanity, or to excesses 

 in the use of alcohol. The subject is not only one of 

 popular interest, but it can be understood by those 

 who are not technically instructed. 



Just as no two men agree in the possession of 

 equally sound mucous membranes or lung tissues, so 

 we may have decided variations in the brain tissues. 

 Together with unsound brain tissue we have symp- 

 toms which we call mental derangement, and of these 

 we have an infinite variety, starting from the mentally 

 too excitable, or too inert, and passing on to those 

 who are more obviously diseased and useless, and 

 finally to those who are dangerous to society at large. 

 Now, these brain affections are markedly hereditary 

 proverbially so indeed. It is true that an overplus 

 of work, or anxiety, or depressing surroundings, may 

 produce insanity or other nervous conditions in one 

 who under better surroundings would undoubtedly 

 escape. These are, no doubt, true exciting factors, 

 but they act with alarming ease in the case of certain 

 types, while in others their action is relatively in- 

 operative. This type, an organic variation, is trans- 

 mitted, it is not destroyed. As Dr. Bastian says: 

 " It is now a well-established fact that persons who 

 are endowed with a neurotic habit of body very 

 frequently transmit a similar tendency to their chil- 

 dren. It is not a tendency to any particular nervous 



