216 



THE EXTERIOR OF THE HORSE. 



elevation of the anterior members, when the animal is in locomotion, 

 becomes exaggerated, — an elevation which is executed at the expense of 

 the length of the step. Whence a loss of time which, insignificant as 

 it may be at each step, eventually determines a marked diminution in 

 the total quantity of speed. 



Direction. — The direction of the arm is indicated by an imagi- 

 nary line which joins the convexity of the great trochanter to the 

 centre of the external lateral ligament of the elb6w. 



It should fulfil the principal elements, as follows : to allow to the 

 scapulo-humeral angle, already reduced by the obliquity of the scapula, 

 a sufficient magnitude, and not to alter the direction of the vertical 

 line in relation with the radius. 



We estimate, from our researches, that a mean inclination of 60 

 degrees is favorable to the development of velocity. When the inclina- 

 tion passes beyond these figures, it must be compensated by an aug- 

 mentation of the scapular obliquity. In the draught-horse, whose 

 scapula is more straight, the humerus does not suffer by becoming more 

 oblique. In the more active draught-horse it is intermediary between 

 the two preceding types. 



The data furnished by instantaneous photographs of animals in 

 locomotion^ show that the limit of extension of the humerus is very 



close to the vertical line passing 

 through the scapulo-humeral 

 centre. 



Theoretically, therefore, 

 the arm should not be too 

 straight at repose, — that is to 

 say, in such a position that the 

 line of direction of the mem- 

 ber is too close to the verti- 

 cal line passing through the 

 centre of the suspension of 

 this member to the trunk. 

 When the conformation is 

 thus, the extension of the 

 humerus is necessarily limited, 

 and such an arm cannot profit 

 by the advantages of a long shoulder. It is true (Fig. 63) that the 

 segment OB', for example, must pass through much less space to 



Fig. 63. 



1 See the figures of MM. Marey and Pag6s, reproducing the details of the oscillation of the 

 members in the gaits. 



