Page:Popular Science Monthly Volume 40.djvu/371

Rh point of the excrescence had been loosed from that part. The formation did not contain any vertebra; the coccyx lay rather beneath, and there was evidently in this, as in a similar case observed by Labourdette, a question of a so-called intercepted formation from the coccygeal lump period. The hide-bound tail offers an enlarged copy of the embryonal coccygeal lump, and exhibits that lump, which in the normal development reverts and is merged in the buttock, apparently maintained and associated, as a rule, with an imperfect development of the anal orifice (Fig. 7).

A third class is composed of the "soft tails," which depend freely from the sacral and coccygeal region and are the most frequent. They have sometimes the form of a swine's tail drawn out to a point; sometimes that of a thicker fleshy appendage only slightly rolled at the end. Such soft tails, which belong to the largest of their kind and are both naked and hairy, have been observed and described, among others by Blancart, König, Elsholtz, Schenk, von Grafenberg, and Greve. The last author sent a tail three inches long (Fig. 8), which he had amputated from a boy eight weeks old, to Prof. Virchow for a more thorough examination, and he found that it was not a simple case of skin formation, but that there lay within the inner cell-texture of the skin a fatty bundle penetrated by large vessels. In this species of malformation—to which the case delineated in Virchow's Archiv für pathologische Anatomie, vol. Ixxxiii, No. 3, seems to belong—we have to do, not with a simple impeded formation, such as the last-mentioned case is considered to be, but with the outgrowth of a part existing in the embryonic plan, which, however, disappears in regular growth, into a monstrosity per excessum, as was the old form of expression. In many respects these cases are atavistic. The