MORBID HEREDITY. 393 



but many persons who exhibit the characteristics of this category 

 have not inherited them. The necessity of this connection between 

 degeneration and heredity ought to disappear along with the 

 notion of inevitable heredity. We may degenerate without a 

 hereditary tendency thereto, and we may escape morbid heredity. 

 Diseases which are developed simply on account of a hereditary 

 or congenital disposition constitute manifestations of a tendency 

 to degeneration. Morel showed long ago that a race of insane, 

 whatever its origin, tends to exhaust itself in the fourth genera- 

 tion. The fact is found to apply to other hereditary diseases. The 

 tendency to become sterile is, like dissimilarity, an indication of 

 the diminishing vitality which constitutes degeneration, and may 

 be found in plant as well as in animal species. Mr. Dixon has 

 shown, as Morel demonstrated for pathological families, that mu- 

 latto stocks die out unless they are crossed with negroes or with 

 whites, and the fourth generation usually marks the limit of their 

 continuance. We have, therefore, a right to infer that it is by 

 degeneration that various diseases which rarely arise except in 

 consequence of a morbid predisposition are met with in the same 

 families. 



Congenital malformations act also frequently like the diseases 

 with which they are found associated. Teratological heredity in- 

 cludes facts very like those which have been marked in pathologi- 

 cal heredity. While we observe such malformations as sexdigit- 

 ism, syndactyly, and ectrodactyly transmitted directly for sev- 

 eral generations, we more usually see different deformities in the 

 same family. This is because the malformation may vary in form 

 and seat according to the age of the embryo in which a disorder 

 of nutrition is produced. It has even been assumed that variation 

 of species may have had a teratological origin ; but we are ac- 

 quainted with very few deformities that have been definitely estab- 

 lished. If the tailless cats of Japan and the Isle of Man are of 

 teratological origin, they constitute a unique exception. While we 

 often observe various deformities in the same family, it is not 

 more rare to meet a number of anomalies in the same person a 

 phenomenon which deserves special attention. 



Most of the deformities compatible with life may be coincident 

 with affections of the nervous system; and the patients whose 

 nervous systems are most gravely affected are just those who pre- 

 sent multiple deformities ; idiots and imbeciles nearly always ex- 

 hibit congenital anomalies, which likewise frequently occur in deaf- 

 mutes, epileptics, etc. The anomalies found in the insane are less 

 gross, but appear more frequently in proportion as the morphol- 

 ogy of that class of patients is more carefully studied. The study 

 of physical anomalies in neuropaths, though they are not less com- 

 mon, is still more frequently neglected. With epileptics who 



