It is necessary to point out that it is not the curves of the three anterior portions of the spinal column which determine the form of the superior border of the neck and shoulders, and of the same part of the trunk. For the first portion, there is a ligament which surmounts the cervical region, and substitutes its modelling influence for that of the vertebræ. It is the _superior cervical ligament_, which arises from the spinous process of the first cervical vertebræ, and is inserted into the external occipital protuberance on the upper part of the posterior surface of the skull. The summits of the spinous processes of the vertebræ alone give form to the superior median border of the trunk. In this connection we here repeat that it is not the general curvature of the vertebral column which produces the withers, but the great length of the spinous process of the first vertebræ of the dorsal region. The Thorax The dorsal vertebræ form the posterior limit in man, and superior in quadrupeds, of the region of the trunk known as the _thorax_. A single bone, the sternum, is situated at the aspect opposite; the ribs bound the thorax on its sides. In its general outlines the thorax in quadrupeds resembles that of man--that is to say, that, as in the latter, the anterior portion--superior in the human being--is narrower than the part opposite. But the progressive widening takes place in a more regular and continuous fashion, so that it presents a more definitely conical outline. This purely conical form is nevertheless found in the human species, but only during infancy; the inferior portion of the thoracic cage being then widely expanded, because of the development of the abdominal viscera, which at that period are relatively large. But the proportionate measurements of the thorax are different. Indeed, we may recall that in man the thorax is flattened from before backwards, so that the distance between the sternum and the vertebral column is shorter than the distance from the rib of one side to the corresponding one of the opposite side (Fig. 5). In animals, on the contrary, it is flattened laterally. Its vertical diameter--measured from the sternum to the vertebral column--is greater than the transverse measurement (Fig. 6). [Illustration: FIG. 5.--A TRANSVERSE SECTION OF THE THORAX OF A MAN PLACED VERTICALLY--THAT IS TO SAY, IN THE DIRECTION WHICH IT WOULD ASSUME IN A MAN PLACED IN THE ATTITUDE OF A QUADRUPED (A DIAGRAMMATIC FIGURE). 1, Dorsal vertebra; 2, sternal region; 3, costal region of one side; 3´, costal region of the other side.]