MUSCLES. 45 



Muscles of the hind limb. — The hip is extended by the great croup 

 muscle, and also by muscles which lie at the back of the thigh bone. One 

 end of the great croup muscle {gluteus maximus) is attached to the upper 

 surface of the front portion of the pelvis, and, proceeding along the side 

 of the sacrum, reaches as far as the last rib. The other end is inserted 

 on the summit of the portion of the thigh bone which projects above the 

 hip joint. The muscles at the back of the thigh bone have their origin, 

 chiefly, on the under surface of the pelvis, from behind the hip joint to 

 the point of the buttock ; and are inserted principally to the lower part 

 of the thigh bone or to the upper portion of the tibia. 



The hip is flexed by muscles that have their origin on the under 

 surface of the loin vertebrae, and are inserted on the thigh bone ; and 

 also by muscles which are attached to the under surface of the pelvis in 

 front of the hip joint, and to the thigh bone, patella, or tibia. 



The stifle is extended by one muscle which has its origin on the under 

 surface of the pelvis, just in front of the hip joint, and is inserted on the 

 patella, and by two others which are attached to the upper part of the 

 thigh bone and to the patella. The first mentioned muscle {anterior 

 rectus) flexes the hip at the same time that it extends the stifle. 



The stifle is flexed chiefly by a muscle which is attached to the portion 

 of the pelvis behind the hip joint, and to the tibia. 



The hock is extended chiefly by two muscles (gastrocnemii) which 

 form the rearmost portion of the gaskin. They have their origin 

 on the lower end of the thigh bone, and are inserted on the point of 

 the hock by their tendons, which lie one over the other, and constitute 

 the tendo Achillis. The underneath tendon terminates at the point 

 of the hock ; but the other is continued down the back of the leg as 

 the rearmost one of the two back tendons, and is inserted on the short 

 pastern bone, as in the fore limb. Owing to the double insertion of 

 this tendon, the hock cannot be extended without the fetlock being 

 flexed at the same time ; hence the success of the plan, for the 

 prevention of kicking, of securely fixing in the hollow of the pastern some 

 hard object of suitable shape, so as to prevent the joint between the 

 two pastern bones from becoming flexed. Extension of the stifle 

 causes extension of the hock. 



The joints below the hock are extended by muscles which take their 

 origin near the stifle joint, run down the front of the hind leg, are con- 

 tinued as tendons down the front of the cannon-bone, and are inserted on 

 the bones of the pastern, and to the front and top of the pedal bone. 



The joints below the hock are flexed by a muscle of the gaskin, which 

 muscle originates at the back of the upper portion of the tibia, behind 

 which it runs down to a little above the hock joint, when it is continued 

 as a tendon that passes over the groove formed on the os calcis. It 

 then proceeds down the back of the cannon-bone, as the front one of the 



