Degeneracy: Its Causes, Signs and Results

by Eugene S. Talbot

FIG. 97.

The ribs and breastbone develop from the processes of the vertebræ. It is probable that every vertebra originally had ribs. Traces of these exist in most vertebræ in the human embryo. In man, as a rule, there are but twelve vertebræ which develop true ribs. In degenerates, as in the gibbon, a thirteenth pair sometimes appears. Normally, the two lowest ribs are, however, very imperfectly developed as compared with the other ten, and one is sometimes absent. The rib develops from the ends of the vertebral bows, which, coming in contact with the muscle plates of their own segment of the body, are by the resulting bulging forced to expand, and later come together through the formation of the breastbone. Checking of these conditions produces various deformities of the chest which have been divided into “funnel-shaped” and “dropper” deformities.[222] Frequently the entire chest wall is arrested early in life (Fig. [97]). The relation between the muscle plates and the course of development of the chest is illustrated by the fact that an arrest of development of important muscles often coexists with deformities of the chest. The human limbs are developments from the fin-folds as found in fishes and the human embryo. In one of these the fins are divided into four segments. The upper segment contains one long bone, the humerus (or arm bone), or the femur (or thigh bone). The second segment contains two long bones, the radius and ulna (or arm bones), or the tibia and fibula (or leg bones). The third segment consists of nine small bones, the carpals of the wrist or the tarsals of the ankle. The fourth segment consists of five separate digits. These limbs pass through three stages in embryonic development as to their position, which may be designated as amphibian, reptilian, and mammalian. Many of these bones fuse together (carpals and tarsals). The digits have long before the late fish stage been formed of more than one bone. At times this condition persists even after the completion of human embryonic development. Limb anomalies resulting from checks of development causing either excess or arrest of development are far from uncommon among degenerates, but are not so common as anomalies of form and proportion. Among such anomalies may be mentioned joined limbs (symelia), or the more or less complete absence of limbs (ectromelia), or the absence of a peripheric segment (hemimelia), or the complete or partial absence of a central segment (phocomelia). Among the other important degeneracies of the limbs are supernumerary digits. These Annadale[223] classifies as: First, a deficient digit loosely attached to the hand or foot or to another digit. Second, a more or less developed digit free at its extremity and articulating with other bones. Thirdly, a fully developed separate digit. Fourth, a digit united along its whole length with another digit. The first three types have been called polydactylia. The last has been called syndactylia. There is finally a condition in which union between the digits results in the disappearance of some of the fingers and toes (Fig. [98]). This condition is called ectrodactylia. Supernumerary digits to the extent of six fingers and six toes are exceedingly common in the families of degenerates. The influence of heredity in this particular has been well demonstrated. The Kelleia family of Malta was one of the earliest reported. The condition may last for five generations,[224] but often disappears on marriage with normal persons outside the community or family. A family of the Arabian Hyabites, named Boldi, confined marriages to their own tribe. They all have twenty-four digits. Children born with a normal number are killed as being the offspring of adultery. The inhabitants of Cycaux, France, till the end of the eighteenth century, had nearly all supernumerary digits either on the hands or feet. Isolated in a mountainous region, they for years intermarried. On communication being opened, they emigrated or married strangers, and sexdigitism vanished. Maupertius reports the case of a German family whose members had twenty-four digits for many generations.[225] One of them refused to acknowledge a normal child. In one instance in the United States supernumerary digits lasted through five generations. A case reported[226] some years ago was the following: The first instance of the appearance of the deformity was in a man, born of a degenerate family in 1752, who had six toes on one foot. His son was born with six toes on one foot, but the daughter was normal. This daughter had five children; among them were a son and daughter, each of whom had six fingers on one hand. The granddaughter had eight children, including one son with six toes on one foot. Another son had two daughters, each having six fingers on each hand, and one daughter having twenty-four digits. This last girl had three children; the son was doubly deformed like his mother, while a second son had six fingers on each hand, the toes being normal. One of the two daughters of the fourth generation (with only the hands affected) had eight children, several of whom were normally developed, but the rest were deformed as follows: One daughter had an osseous thickening at the end of the digits, one son had twenty-four digits, another had twelve fingers, the toes being normal in number.

FIG. 98.

FIG. 99.

I have elsewhere cited an instance from Kiernan in which unilateral sexdigitism was found in four generations of Norwegian degenerates.

Not unfrequently polydactylia is associated with the absence or union or decrease in size of bones of the limbs. It happens that the upper or lower extremities may be increased or diminished disproportionately through the body. This disproportion in size of the fingers and toes is exceedingly frequent. Big digits (macrodactylia, Fig. [99]) are comparatively rare, and may only involve a supernumerary bone in the thumb. Short digits (microdactylia) are much more frequent. This state may be constituted by the absence of one bone or the union of two bones, or the shortening of metacarpal or metatarsal bones, or the shortness of several phalangeal bones. There may be increased disproportion between the different fingers. The method of determining this is by comparison with the middle finger. This disproportion may vary greatly. Féré is of opinion that shortening of all the fingers constitutes a grave mark of degeneracy. Relative shortness is exceedingly common.