MUSCLE 237 



progression of the hoof is a straight Hne and the full force 

 of the thrust is obtained in moving the mass of the body 

 forward. 



When the conformation deviates from this standard, as in 

 fig. 119, B, C, D, the line of progression of the foot is in 

 segments of circles. Part of the force is lost and the hoof, 

 or in the shod animal, the shoe, wears unevenly. 



The shape of the hoof and the slope of the phalanges 

 are of great importance. The slope of the wall of the hoof 

 and of the phalanges should be the same — about 45° to 50° 

 in the front foot, and about 50"^ to 55^ in the hind foot. 

 When the phalanges are too perpendicular, as in the " upright 

 pastern" or "boxy foot" (fig. 120, A), the concussion absorbing 

 mechanism is less eftective, as more of the shock is trans- 

 mitted direct from the third phalanx to the second. When 

 the phalanges are too obliquely placed (fig. 120, C) undue 

 strain is thrown upon the tendons and ligaments supporting 

 the sesamoid bones. These are consequently more liable to 

 injury. A high heel is usually associated with upright 

 phalanges and a low heel with sloj^ing phalanges. 



The more upright the foot the shorter and lower the 

 stride. Fig. 120 illustrates how the course of the flight of 

 the foot is determined by its shape. 



(2) Action of the Limbs, 



(1) In standing the weight of the body is chiefly slung by 

 the serrati magni on the scapulas, which are supported by 

 the bony columns of the fore limbs. The flexor and 

 extensor muscles maintain the condition of partial flexion 

 at the elbow joint. The metacarpo-phalangeal articulation 

 (the fetlock joint) is supported chiefly by the tendons of the 

 flexor muscles and by the interosseus muscle (the suspensory 

 ligament). This is a muscle which has become tendinous in 

 form and function. By it the sesamoid bone is suspended. 



The tendons of the flexor muscles, which are the chief 

 supports for the fore legs, are connected to the bony column 

 by fibrous bands (the check ligaments). These act as 

 mechanical stays to the limb, relieving the muscles from 



