THE SKELETON 
THE VERTEBRAL COLUMN 
THE vertebral column of an adult human being consists normally 
of thirty-three to thirty-four vertebre, numerical variation being 
due to the inconstancy of those of the coccygeal or caudal series. 
As might be expected from the study of other related organs (¢.g. 
the vertex coccygeus, the filium terminale, the arteria sacralis 
media, certain muscles and nerves, and the coccygeal gland), 
we here meet with evidence of degeneration and variation. This 
is specially the case during development. It is, above all, the 
caudal region which, in this respect, has claimed the greatest 
attention of morphologists; and incidentally to the study of this 
there arises the old controversy as to whether Man or his 
ancestors possessed a tail. 
At an early stage of development the human embryo 
possesses at the posterior end of the body, clearly in direct 
continuity with its developing axial skeleton, a free projecting 
pointed appendage, bearing an undeniable resemblance to the tail 
of a lower animal. This is delineated in Fig. 17, ed., and will 
be further discussed as we proceed. At later stages of develop- 
ment this organ is less conspicuous; it gradually becomes shorter 
and blunter, and is slowly, as it were, taken into the trunk. 
For some time, however, a caudal prominence remains; but 
this at last either disappears altogether, or leaves, at the point 
where its tip abutted against the integument, more or less 
distinct traces known as the “vertex coccygeus” (ch ante, 
pp. 5 and 7). This is the normal course of development, but 
occasionally a tail-like appendage is found in extra-uterine life. 
An extensive literature exists on this subject) and to it I 
1 Some of the alleged observations on this subject are not such as to awaken 
confidence, and others refer to pathological cases or abortions, in which, among 
other malformations, more or less developed caudal appendages occurred. Other 
