228 THE TRUNK. 



consideration of the conformation of the chest, which is 

 influenced chiefly by the shape, size and setting-on of the 

 ribs. The points which we should seek for in the ribs 

 of a horse, in order to obtain the best possible breathing 

 power, are : — 



1. Convexity (roundness) of ribs (" barrel ") behind the 

 shoulders. 



2. Good length of ribs. 



3. Ribs well inclined to the rear. 



The convexity of a curve may be measured by the 

 proportion which its height (c d, Fig. 313 or Fig. 314) 

 bears to the length of its chord a b. Thus, if c ^ is 

 equal to | « 6 in Fig. 313, and equal to ^ a b in Fig. 

 314, the curve a c b will be three times as convex in the 

 former as in the latter. 



Among the higher animals, we find that chest capacity 



c « , 



Fig. 313. — Semi-circle. Fig. 314. — Arc of Circle. 



is obtained either by convexity or by length. Hence, 

 animals which have short chests have round ones, and 

 those that have long ones have them flat-sided, the capacity 

 being increased by roundness of the ribs and decreased 

 by flatness of these bones. We have already seen that 

 undue length of body is detrimental to speed, weight- 

 carrying power, and strength in draught. Consequently, 

 we should seek for roundness of chest in order to obtain 

 good breathing power Youatt, in his book on The Horse, 

 appears to have originated a fallacy concerning the con- 

 formation of the ribs which has been • repeated by many 

 English writers. He says that " the circular chest could 

 not expand, but every change of form would be a diminu- 

 tion of capacity." This statement seems to be based 

 on the supposition that the chest expands and contracts 

 by the ribs opening and closing in a direction at right 



