158 THE EXTERIOR OF THE HORSE. 



Through the bony parts, it is primarily an apparatus of protection to the 

 central organs of respiration and circulation. By the mobility which it possesses, 

 it constitutes the most important agent in the respiratory mechanism. Finally, 

 by its resistance, its connections with the spine, and the extent of its skeletal 

 surface, it plays an important role in locomotion by furnishing numerous points 

 of attachment to the muscles which belong to the superior sections of the thoracic 

 members. To fulfil this last purpose, its first pieces are short, strong, straight, 

 and but slightly movable, for their action woi^ld be very much disturbed by their 

 relation with the shoulder and arm. The last pieces, on the contrary, are 

 curved more and more, narrower, removed from the median plane, and leave 

 .a wide space at the posterior part of the pulmonary lobes. 



Beauties. Although the chest-wall is far from being observable 

 over its whole extent from the outside, it is possible to judge of its 

 capacity with much precision. This knowledge is of the greatest im- 

 portance, for it furnishes information upon the essential elements of the 

 value of the horse. 



The chest may be called beautiful when it is high, wide, and long. 

 Let us see the meaning which should be attached to these three words : 



1st. Height. This is measured from the summit of the withers 

 to the inferior surface of the xiphoid region ; this line, then, marks 

 the true vertical diameter of the thorax, that diameter being greatest at 

 the spinous process of the fifth dorsal vertebra, which forms, as we have 

 seen, the culminating point of the withers. 



This dimension must not be confounded with the depth, which is 

 measured from before to behind ; it is to be regretted that some hip- 

 potomists have changed, in this connection, the meaning of a term 

 established by long usage. 1 



In speaking of the ribs, we have said that this height, with the 

 corresponding width, is directly proportional to the length of these bony 

 arches. When this height is considerable, the chest is said to be well 

 descended, an epithet which depicts its situation relative to the ground. 



We must remember, moreover, that the extent of this thoracic 

 dimension is one of the conditions of pectoral amplitude. It should, 

 however, not be forgotten that this factor alone is insufficient to the 

 development of the thoracic capacity ; the curvature of the ribs must 

 also be taken into the reckoning. Leaving out of the account the 

 length of the fifth dorsal spinal apophysis, the height of the chest is 

 nothing else than the chord of the arch represented by the ribs. Mere 

 height of the chest has no longer any importance but for the coexistent 



1 The depth of a thing, says Littre, is the extent of this thing, considered from its entrance 

 to its bottom. The entrance of the chest is situated between the first two ribs; its bottom is the 

 diaphragm. Therefore, here, depth is synonymous with length. 



