ANTERIOR MEMBER. 



207 



Direction. Another element in the beauty of the shoulder of the 

 race-horse in particular resides in its obliquity. 



This direction is indicated by an imaginary line which passes from 

 the summit of the withers through the centre of the scapulo- 

 humeral articulation. Observation has demonstrated that this line 

 passes a little posterior to the scapular spine. 



Marked obliquity of the shoulder has always been considered a 

 beauty, or point of excellence, in 

 close relation with the production 

 of speed ; while in its relation with 

 the development of force it is com- 

 paratively indiiferent. Nothing is 

 more easy of comprehension. 



Let us represent (Fig. 59) OA and 

 OA / , two shoulders of unequal obliq- 

 uities, and OS, the humerus on which 

 they operate. Let us suppose, also, that 

 A OB' be the maximum opening of the 

 angle AOB. 



All things being equal, the limit of 

 extension of the humerus on the shoul- 

 der OA' will be carried to B", since, 

 from the anatomical union of the two 

 regions, the angle A / OB" is equal to the 

 angle A OB'. (See Generalities on the Mem- 

 bers, p. 194.) OB" being more distant 

 from the vertical line than OB', will also be 

 relation with the vertical direction OX. 



FIG. 59. 

 favorably directed than OB' in 



The orientation of the scapulo-humeral angle is therefore most 

 favorable to progression when the shoulder is oblique; the inferior 

 segments of the member are further advanced, and such a shoulder 

 especially if it be long will be capable of producing a much more 

 extensive revolution of the humerus BB f . 



If, instead of becoming larger from the straightening of the 

 shoulder, the scapulo-humeral angle remains the same (A' OC= AOB\ 

 it is correct to assume that, from an equal functional shortening of the 

 muscles, the humerus O C will be carried less in advance than the 

 humerus OB. 



Such are the reasons which operate in favor of a great obliquity in 

 horses of speed ; but this is not all. 



If we study the movements of the shoulder, viewed separately, the 

 fact becomes evident that, for an equal elevation of its extremity, it will 



