558 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1918. 



in which such conditions occur with great frequency for many 

 generations. Some members of such a stock may be epileptic, others 

 suffer from insanity or marked moral failing, while others may be 

 feeble-minded or even idiots. Since the environment of such per- 

 sons differs in no material particular from that of the mentally 

 healthy section of the community among whom they live, it is clear 

 that the failing is of the germ cell and is inherited. In many 

 family histories it is possible to trace a definite progressive accentu- 

 ation of the impairment, and in some even to trace it to its origin. 

 Thus, in persons suffering from the mildest manifestations, neuro- 

 pathic antecedents are relatively uncommon; but a history of an- 

 cestral alcoholism or tuberculosis is frequently found. Among 

 epileptics, evidence of the neuropathic diathesis occurs in about 35 

 per cent of cases; in the insane this proportion reaches from 50 to 

 60 per cent; while in the mentally defective it occurs in from 80 

 to 90 per cent. There is thus an increasing degeneracy, which 

 reaches its culminating point in that condition in which mind has 

 become so reduced as hardly to have an existence, namely, profound 

 or absolute idiocy. 



It has sometimes been objected that, since the particular defect of 

 the individual is not identical with that which has existed in his 

 ancestors, it can not be regarded as "hereditary." This, however, 

 is either mere hair splitting or betokens a complete ignorance of the 

 nature of the inheritance underlying these morbid conditions. Of 

 course idiocy, insanity, epilepsy, etc., are no more inherited, as such, 

 than any other human quality or defect. Inheritance consists, not in 

 the transmission of actual qualities as we see them, but in the poten- 

 tiality to develop those qualities under an appropriate stimulus. 

 Similarly in degeneracy, what is transmitted is not epilepsy, in- 

 sanity, or mental defect, but a diminished developmental potentiality 

 of the nervous system; in other words, the neuropathic diathesis; 

 and I am of opinion that here also the particular manifestations are 

 in many cases determined by particular environmental factors oper- 

 ating during the period of growth. 



It has been stated that the gross forms of mental defect represent 

 the culmination of degeneracy ; and hence it follows that individuals 

 so suffering are usually characterized by serious abnormalities of 

 anatomical growth and of physiological function in many parts of 

 the body. These are known as " stigmata of degeneracy.' 3 The list 

 of these "stigmata" is a long one, comprising among others, de- 

 formities of the brain, eyes, external ears, nose, palate, hands, feet, 

 and many other structures. I must confess that the inclusion of 

 some of the anomalies which have been described amongst the signs 

 of " degeneracy " (as I have defined it) seems hardly warranted. 



