154 THE EXTERIOR OF THE HORSE. 



complete similarity may not be possible, on account of the irregularity of their 

 curvature and the variations of their length and form. 



Henry Cline long ago demonstrated 1 that the more the pectoral 

 cavity deviates from a cylindrical form the more its capacity is di- 

 minished. It results from this that the rib which presents the greatest 

 curvature will also be the one which circumscribes the greatest space. 

 Depress a cone or cylinder, and the reduction of their volume is in pro- 

 portion to the flatness of their surface. The thorax may be regarded as 

 a flattened cone ; and this is why we say : for an equal length of the ribs, 

 the chest can never gain in height what it has lost in width ; or, in other- 

 words, the convexity of the ribs is the first beauty, or point of struct- 

 ural merit, to be sought for in a good conformation of this region. 



2d. This is not all^ the ribs, as structural elements of the costal 

 region, should also be llSlg, for this length of ribs constitutes, for an 

 equal width of the chest, the thoracic measurement in the vertical sense. 

 The volume of a solid depends upon the relation which exists between 

 its three dimensions ; to be large, it is necessary that the dimensions 

 should all be as large as possible. 



It is, however, interesting to know that the rib can make up by 

 its length for the lack of chest-volume occasioned by its loss of con- 

 vexity. This proposition, which appears to be contradictory, in prin- 

 ciple, to that which we have just given above, is, however, very logical, 

 as we shall see. 



In the preceding case we supposed the length of the rib invariable^ 

 and only made its curvature variable. In the present case we inves- 

 tigate the problem under its two aspects by modifying its data to find 

 the compensations, if any exist. This method can be illustrated by the 

 following comparison : Is there for two horses, the one having very 

 round ribs and a low chest, the other, less convex ribs and a very high 

 chest, any compensation in respect to the thoracic capacity ? 



Nearly all authors answer this question in the affirmative, and,, 

 theoretically speaking, they are correct. 



Let us suppose the two ribs A OB and ADC (Fig. 44). Let us also remem- 



ber that they have not the same convexity, since the ratio is greater than , 



AB AC 



which indicates that the first is more curved than the second. 



A glance at the figure shows that not only does the rib ADC circumscribe a 

 surface equal to that of the rib AOB, but one that much exceeds the latter. 

 Here, then, are two animals having the same width of the chest and a different 

 convexity of the ribs, for which there is more than a compensation. Another 



1 Henry Cline, Trait sur la forme des animaux, published in the work of M. G. Lefevre de- 

 Sainte-Marie : De la race bovine courte corne amelioree, dite Race de Durham, Paris, 1849, p. 325.. 



