40 SKETCH OF THE ANATOMY OF THE HORSE. 



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 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, for the most part, by muscles which form the rear- 

 most portion of the gaskin (" second thigh "). They have their origin on the 

 lower end of the thigh bone, and are inserted to 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 can- 

 not be extended without the fetlock being flexed at the same time ; hence 

 the success of the expedient, 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. 



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 highest point of the cofiin 

 bone. 



The joints bcloiv 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 two back tendons, 

 and terminates in the same manner as in the fore limb. The muscle of the 

 rear back tendon, as we have already seen, also aids in flexing the fetlock 

 and pastern joints. 



Heart and Lungs. — The heart is a hollow muscle which acts as a 

 force pump in sending the blood through the arteries to the various parts 

 of the body. The arteries commence on the left side of the heart, by 

 one large trunk which splits up, as it goes on, into an innumerable number 

 of small branches, that, as a rule, terminate in a microscopic network of 

 minute canals called capillaries. These canals, which probably do not 



