MUSCLE 239 



strain when the standing position is long continued. A Hke 

 arrangement of mechanical braces exists in the hind limbs. 



The centre of gravity is in a vertical plane passing about 

 6 inches behind the elbow. In standing, therefore, the 

 greater weight, some 10 to 20 per cent, more, is borne by 

 the fore legs than by the hind. The proportion depends 

 largely on the position of the head. As the head comes 

 down and forward as in sleep, the centre of gravity moves 

 forward, and the proportion of weight carried by the fore 

 legs is increased. 



In standing for any length of time the hind legs are used 

 alternately to support the weight of the posterior part of the 

 body, the one not in use being partly flexed and resting on 

 the toe. From the fact that the hind leg^s are less straicfht 

 than the fore legs, more work is required by the leg muscles 

 in using them as supports. 



2. Lying. — Owing to the sharp edge of the sternum the 

 horse cannot lie vertically. It either lies inclined to one 

 side with the four feet tucked under the body, or flat on the 

 side with head and legs extended. 



3. Rising. — In rising the head is raised, the fore feet are 

 placed on the ground in front, and the hind legs are placed 

 well below the body and push it up. The raising of the 

 head is the first part of the act of rising, and if it be kept 

 down the animal cannot rise. 



4. The movements of the horse at the different paces 

 have been analysed by instantaneous photography. 



Walk. — The body being balanced on three legs, as shown 

 in fig. 121, one fore leg is advanced, the body moves forward 

 on the corresponding hind leg, and the opposite hind foot 

 leaves the ground before the fore foot reaches it, so that for 

 a moment the horse is balanced on diagonal legs (2). The 

 hind foot which has left the ground is now advanced, and 

 before it is planted the corresponding fore foot is lifted (3), 

 and thus, at this stage, the animal is balanced on the fore 

 and hind leg of the same side (4). As the hind foot comes 

 to the ground, the condition described at the starting is 

 again reached and the process is repeated. 



Normally in walking the heel comes first to the ground. 



