DEGENERACY TREDGOLD. 557 



comparatively little change with the evolution of the human race 

 through many lower species. There are others, such as the nervous 

 system, which have undergone a very great elaboration, probably 

 even in man himself. It is legitimate to conclude that the innate 

 germinal potentiality of the systems of less antiquity, which have 

 undergone more recent evolutionary change, will be more liable to 

 alteration under adverse or abnormal conditions of the environment 

 than will the potentiality of those which are more organically fixed 

 and have, in fact, a longer heritage; and hence it will come about 

 that these adverse factors exert a selective influence upon the con- 

 stituents of the germ cell, being chiefly operative upon the higher 

 parts of the nervous system. At the same time our conception of 

 development can hardly be that of a series of organs each pursuing 

 its own growth independently. It seems likely that a certain 

 mutual interrestraint exists, and that, where the potentiality for 

 growth of one organ or tissue is rendered defective, the lessening of 

 restraint may result in irregularity and overgrowth of contiguous 

 tissues, with the production of gross anatomical anomalies and de- 

 velopmental errors. 



When we turn to the manifestations of degeneracy — that is, to 

 the manner in which these pathological variations of the germ cell 

 are revealed in the offspring — we find strong corroboration of these 

 views. Eetrogressive variations, manifested generation after gener- 

 ation, are to be found, it is true, in many organs, such as the skin, 

 the eyes, the skeleton, etc. ; but the commonest expression of all and 

 by far the most frequent form of degeneracy is seen in a defective 

 and abnormal constitution of the higher parts of the nervous sys- 

 tem; that is, in the parts concerned with the functions of mind. 

 The usual medical term for this manifestation of degeneracy is 

 " neuropathic diathesis " ; and its physical basis is undoubtedly, as 

 has now been shown by many exhaustive inquiries, an impairment of 

 neuronic potentiality which is germinal in origin and may be trans- 

 mitted generation after generation. 



The manifestations of this neuropathic diathesis vary greatly in 

 their degree and nature. In the slighter forms of impairment, as 

 already remarked, there is simply a lessened durability and dimin- 

 ished power of resisting the stresses and strains of life ; a weakening 

 of nerve vigor, a proneness to psychasthenia, and a consequent 

 inability for sustained competition. If more pronounced, there is 

 a tendency to early mental dissolution or dementia, to hysteria, 

 epilepsy, insanity, and other marked psychopathic disorders; while, 

 if still more marked, there are grave defects of anatomical develop- 

 ment, resulting in feeble-mindedness, imbecility, or idiocy. It has 

 now been conclusively shown that, while some stocks evince no 

 tendency to any of these abnormal mental states, there are others 



