PHYSIOLOGY OF MOVEMENT. 



735 



Below the humerus the bones lie, with the exception of the phalanges, 

 in an almost vertical line, flexion being prevented by the five extensors 

 of the forearm. The metacarpus continues the vertical column of which 

 the forearm forms the superior segment, its flexion being prevented by 



Fig. 298.— Anterior Extremity op the 



Horse in Extension. (Colin.) 



AD. BD, and CD, lines of action of the triceps exten- 



eorbrachii.seapulo-ulnaris, and aconeus muscles. E F, 



flexor brachii. G H, line of action of flexor pedis mus- 



Fig. 299.— Posterior Extremity of the 

 Horse in Extension. {Colin.) 

 AB, line of action of gluteus medius. CD. line of 

 action of triceps extensor. E F, line of action of gas- 

 trocnemius. G M, line of action of metatarsal flexor. 



the extensor inserted in its carpal extremit}', and which receives in about 

 the middle of its fleshy belly an aponeurotic cord fixed superiorly to the 

 external tuberosity of the humerus. In the phalangeal region the direc- 

 tion of the bony support now becomes oblique, and, while its obliquity 



