OSTEOLOGY AND ARTHROLOGY 13 



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 ab- 

 dominal 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 correspond- 

 ing 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). 



Fi-G. 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). 



I, Dorsal vertebra; 2, sternal region; 3, costal region of one side; 

 3', costal region of the other side. 



From this results a peculiar arrangement of the muscles 

 that we are able to bring directly into prominence, which 

 presents points of interest from the point of view of the con- 

 traction of the subcutaneous layer. Indeed, in man the 

 region occupied by the pectorals is very broad ; it is a wide 

 surface turned directly forward. In quadrupeds, this region 

 of the pectorals is narrowed. It is not spread out, as in the 

 preceding instances ; and the appearance it presents is 

 explained by the fact that the thorax is compressed laterally. 

 If we examine the thorax on one of its lateral surfaces, the 

 muscles, on the contrary, are more extended. We see the 

 contour of the vertebral column, and the median part of the 

 abdomen ; and, especially in the horse, between the great 



