Page:Popular Science Monthly Volume 40.djvu/368

354 again after the thirtieth year of age. Mr. Tait believes that the hollow is associated with the embryonal process connected with the neural canal and its closure. He referred to the tailless cats of the Isle of Man, and tailless guinea-pigs which, like man, possess only an os coccygis with three pronged centra infolded in the skin; and thought that he might conclude from certain indications that some of these animals, and perhaps also the predecessors of man, may have lost the tail in consequence of a malformation, probably in man through the not rarely appearing spina bifida. We well know how such malformations tend to become hereditary; and the sacral dimple might be called the scar of the lost tail. The hereditability of such malformations is well marked. When Dr. Wilson crossed a Manx tomcat with a common cat, seventeen out of twenty-three kittens were tailless; but when female cats of the Isle of Man were crossed with common tomcats all the kittens had tails, though somewhat shortened. Prof. Ecker has suggested a less fanciful explanation of the origin of the sacral dimple. He supposes that the later inward curving of the tip of the much straighter coccyx in the fœtus—which is connected with the skin by the caudal ligament—draws the corresponding spot on the skin into a funnel shape of greater or less depth. On the other hand, Ecker would rather regard the glabella coccygea as the lower fontanel, or later point of closure of the sacral canal.

The embryonal processes and normal conditions of formation thus briefly sketched are sufficient in general to permit most of the cases of so-called tail-formations in men, which occur with tolerable frequency, to be recognized as easily explainable irregularities of natural growth. The case deviating least from the normal condition concerns only the skin-covering, and exhibits itself in an excessive hairiness of the sacral and coccygeal region (trichosis sacralis). We have seen above that this spot in the embryo reo-ularly bears a hair-twirl, which is not rarely prolonged into a hairy pencil or taillet. We can hardly consider it an important variation if this hairy taillet is exceptionally not absorbed, but endures and grows stronger after birth. In the so-called hairy men we evidently have persons in whom, according to all appearance, the wool-hair of the fœtus has grown to a far greater extent, or at least possesses the same properties of alignment and direction. The chief physician of the Greek army, Dr. Bernhard Ornstein, having observed several cases of extraordinarily abundant hairiness in the sacral region among Grecian recruits, has given continued attention to this phenomenon, and has determined some very remarkable cases of it. The most striking of these cases was that of the twenty-eight-year-old recruit Demeter Karus, of the eparchy of Corinth. The whole sacral region appears to be