260 THE EXTERIOR OF THE HORSE. 



e, of the {rochanter, or on the summit, c, of the patella, is communi- 

 cated also in the same sense and with an equal intensity to the summit, 

 a, of the calcaneus. 



It is thus that, in spite of their distance of separation, the exten- 

 sors of the femur and of the tibia participate in an indirect manner 

 in the extension of the canon, — that is to say, in the maintenance of the 

 tibio-tarsal angle, owing to the mechanical role of the cord of the hock. 

 This remarkable synergy or correlation in the extension of the articular 

 angles of the posterior limb explains the vigor, precision, and sudden- 

 ness of the propulsive movements of this member during locomotion. 

 It also accounts for the true action of the gastrocnemius, the perfor- 

 atus, and part of the tibial aponeurosis, which thus become agents of 

 transmission in common with the muscles of the croup, the stifle, and 

 the leg, enormous muscles, acting together and simultaneously to over- 

 come the inertia of the body and to j^ropel the latter forward. 



Thus the organization of this cord responds admirably to the 

 function which is allotted to it. Being composed of two voluminous 

 tendons, that of the perforatus and that of the gastrocnemius, twisted 

 one upon the other, reinforced by a thick lamina of the tibial aponeu- 

 rosis, and, finally, attached to the summit of the calcaneus, this cord 

 acts, besides, almost perpendicularly to the extremity of one of the 

 longest lever-arms in the economy. The tarsus, from the number of 

 its bones, the smallness of their dimensions, the strength of their 

 means of union, the tenuity of their movements, becomes finally the 

 instrument which receives the force, transmits it, attenuates it, dis- 

 perses and decomposes it without inconvenience to the living machine, 

 on condition, however, that this base be constituted according to the 

 mechanical principles which we are about to explain. 



Beauties.— The hock, to be well formed, sliould be neatly outlined, 

 lean, wide, thick, well opened, and inell directed. 



Neatness of Outline.— The hock is said to be neat and nicely 

 cut out when it reproduces exactly the shape which we have described 

 above. It is, in this case, exempt from blemishes, and its hollow is 

 very pronounced. 



Leanness or Dryness. — This region is, moreover, qualified lean 

 or dry when all its normal elevations and depressions are well marked 

 and covered by a fine, supple skin, adherent to the adjacent parts. 

 The neatness of outline indicates the soundness of the pieces of the 

 tarsal apparatus; its leanness, on the contrary, implies the pureness of 

 the breed, the fineness of the constitution, and the energy and excita- 

 bility of the individual. In subjects of a lymphatic temj erament, as 



