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 

 tlie development of force it is com- 

 paratively indifferent. Nothing is 

 more easy of comprehension. 



Let us represent (Fig. 59) OA and 

 OA', two shoulders of unequal obliq- 

 uities, and OB, the humerus on which 

 they operate. Let us suppose, also, that 

 AOB^ be the maximum opening of the 

 angle A OB. 



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 0B\ (See Oeneralities on the Mem- 

 bers, p. 194.) OB^' being more distant 



from the vertical line than 0B\ will also be less favorably directed than OB^ in 

 relation with the vertical direction OX. 



Fig. 59. 



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'. 



If, instead of becoming larger from the straightening of the 

 shoulder, the scapulo-humeral angle remains the same {A' 0C= AOB), 

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

 muscles, the humerus OC 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 



