136 THE HORSE 



to the hip joint, which is also a ball-and-socket joint, but 

 it differs from the shoulder joint in one remarkable 

 respect, namely, that there is a short round ligament — 

 (the so-called round Hgament) — which passes between 

 the articular head of the first thigh bone and the cavity 

 into which it fits on the pelvis. This exercises a restrain- 

 ing movement by preventing abduction of the limb. 

 This ligament is practically absent in cattle, hence the 

 reason these animals are able to kick in an outward 

 direction as well as backwards and forwards. 



The shoulder joint of the horse, as previously stated, 

 allows a great freedom of movement, and this is super- 

 added to by the manner in which the scapula or shoulder- 

 blade is slung on to the side of the chest wall. All joints, 

 in addition to being enclosed by a capsular ligament, 

 have the ends of the bone covered by cartilage, whilst 

 the capsular ligament is lined by synobial membrane, 

 the special functions of which are to secrete synobia, or 

 what is popularly known as joint-oil — an albuminous 

 fluid allied to the white of egg. 



From what we have already said the reader will have 

 learned how a joint is formed. Following upon the 

 shoulder joint is the elbow joint, and this is quite different 

 from the first named. To begin with there is practically 

 no lateral movement, this being what is known as a hinge 

 joint, and is formed by the union of three bones, namely, 

 the lower end of the humerus, the upper end of the 

 radius, and the articular surface of the ulna. Extension 

 is the principal movement of this joint. 



Succeeding the elbow joint we come to the so-called 

 knee, which is composed of a number of small bones, each 

 having several minute articular surfaces or facets for 

 articulation amongst themselves, and conferring upon 

 them a slight gliding movement. In reality the knee 

 joint is a complex one. Thus, for instance, there is that 

 formed between the lower end of the radius and the 

 upper row of the carpal bones, constituting the so-called 



