Ixxxii INTRODUCTION. 



tebral column, acting upon the pelvis and thighs ; and a 

 set extending backwards cause the motions of the tail and 

 other parts. The ribs are connected together, and moved, 

 by numerous muscles passing between them ; and the abdo- 

 men is covered by flat tendinous muscles, which support 

 the contained viscera. The diaphragm, extending within 

 the trunk from the spine to the breast-bone, separates the 

 cavities of the chest and abdomen. The hinder extremities, 

 which are the main instruments of progression, are moved 

 by muscles of prodigious force, connected with the spine, 

 sacrum, and bones, of the pelvis, giving motion to the thigh 

 and leg. One set is employed in bending the limb under 

 the body, another in extending it backwards. The muscles 

 which extend downward to move the lower part of the limb, 

 becpme tendinous as they descend, until, having reached the 

 hock, they are almost wholly tendinous. By this mechanism 

 the various pieces of the limb are either flexed or extended, 

 without loading with muscle the parts to be pulled. 



The fore extremities are moved by a series of muscles at- 

 tached to the shoulder-blade, and by others, extending from 

 the higher parts of the limb downwards. These last, like 

 the muscles of the hinder extremity, become tendinous down- 

 wards, until, at and below the knee, they are almost wholly 

 tendinous. They are distinguished into those which extend 

 the humerus and other pieces of the limb forwards, and 

 those which bend them backwards. The parts of the limb 

 being extended, and at the same time bent, the limbs clear 

 the ground, when the animal is propelled forwards. In 

 order that they may be raised sufficiently to clear the ground, 

 and move in harmony with the hinder limbs, there must be 

 a peculiar adaptation of parts, and fitting strength of muscle. 

 The due performance of these functions constitutes chiefly 

 what is termed action in the horse, and we judge essentially 

 of his safety and usefulness from the form and movements 

 of his fore-extremities. 



The horse, when we regard him in profile, is compre- 



