Under the conditions of development of the limbs from the fin-fold, it follows that these may be checked completely so that the condition approximates the earlier development from the fish. On the other hand the large bones of the arm and thigh may be checked while the digits and the two lower bones (radius and ulna, tibia and fibula) go on to full development as do the digits. Sometimes the arms develop completely while the lower extremity remains in the fin-fold state. On the other hand the arms may be checked and remain in the fin-fold state while the legs go on to full development. Sometimes the bones of the arm and forearm are checked while the digits go on to full development. The lower extremities are sometimes fused together. This condition, from its resemblance to the like state in the seal, is called phocomelia, or seal limbs. They are also called sirens, on account of the resemblance to the sirens of mythology.[227]
FIG. 100.
Other expressions of degeneracy, albeit sometimes secondary, are club-foot and club-hands (Fig. [100]). In many instances these are retentions of positions assumed by the limbs of the fœtus in the course of evolution, and are therefore, in the adult, expressions of degeneracy. Club-foot was an expression of degeneracy which appeared in Byron, the poet, as a consequence of the degeneracy present in both the Byrons and the Gordons, as Kiernan has shown.[228] Commenting on this condition as found in Byron, F. S. Coolidge, of Chicago, remarks: “Byron undoubtedly suffered from double congenital club-foot, the deformity being worse on the right.” While in Coolidge’s opinion congenital club-foot unquestionably arises from different causes, it is, however, so frequently an accompaniment of severe forms of mal-development and of congenital brain defects, that there can be no doubt but that imperfect constitutional development is one of its causes. That the deformity with the many limitations which it involves may tend to create morbidness is very likely to be an additional symptom of the degeneracy which, in certain cases, is the underlying cause for the deformity. Dareste, who has studied the club-foot and the club-hand from the standpoint of experimental teratology, finds that in no small number of cases club-foot and club-hand result from checked development. Absence of the kneecap or patella may, as H. N. Moyer has shown, be an expression of degeneracy.[229]
The conditions resultant on checked development may appear in any of the bony or muscular structures. At times muscles checked in development pass on to conditions present in the lower apes.[230] Sometimes the checked development of bones results in artery courses which are present in some of the lower animals. Just above the bend of the elbow in the embryo is an opening through which an artery passes in many quadrupeds. In adult man, as a rule, this has disappeared, but not rarely in degenerates the opening persists with the artery through it.
Hernias, of all varieties, are noticeably hereditary,[231] but what is hereditary is not the rupture, but the laxity of the orifice of the cavity of the abdomen. As descent of the testicles from the abdomen (where they are embryonically in man and normally in many animals) is often delayed and even does not occur in degenerates, hernia of the groin variety is particularly apt to occur in them. These hernias are often found united with defects of the testicles as well as deficiencies of the chest. Deformities of the nose are also especially apt to coexist with these.
Degenerate women frequently have supernumerary milk glands arranged on the abdomen as in some lemurs, while males may have supernumerary breasts of either male or female type. These breasts may be represented by nipples alone. In either sex arrested development of the face, middle ear, and palate often coexists with these supernumerary breasts.
The degeneracies of the body combine so frequently with those of the skull and the brain as to indicate a common origin. Polydactylia is found with almost all the degeneracies of the body. It occurs with all the degeneracies of the eye, from those which are purely atavistic like coloboma to those like retinitis pigmentosa and amauroses, which are atavistic in origin. Hare-lip, cleft palate, and deformities of the jaws and teeth are often found associated with all the bodily degeneracies and the nutritive, intellectual, and moral degeneracies as well. Phocomelia with brain deformity has been found associated with them. Anomalies of the genital organs are also quite frequently associated with these and with finger anomalies. In the subjects of juvenile obesity are frequently associated unstable mentality and will-power, and delayed or precocious sexual maturity. My own observations have shown this condition to be frequently associated with the jaw and teeth degeneracies.