302 DISEASES OF THE HOBSE. 



form, being in one case compuiiitively flat and another elevated; or 

 as forming a protruding head or knob, with a distinct convexity; 

 and again presenting a corresponding depression or cavity, accu- 

 rately adapted to complete, by their coaptation, the ball-and-socket 

 joint. The articulation of the arm and shoulder is an example of 

 the first kind, while that of the hip with the thigh bone is a perfect 

 exhibition of the latter. 



The structure whose office it is to retain the articulating surfaces in 

 place is the ligament. This is usually a white, fibrous, inelastic 

 tissue; sometimes, however, it is elastic in character and yellowish. 

 In some instances it is funicular shaped or corded, serving to bind 

 more firmly together the bones to which its extremities are attached ; 

 in others it consists of a broad membrane, wholly or partially sur- 

 rounding the broad articulations, and calculated rather for the pro- 

 tection of the cavity from intrusion by the air than for other security. 

 This latter form, known as capsular, is usually found in connection 

 with joints which possess a free and extended movement. The 

 capsular and funicular ligaments are sometimes associated, the cap- 

 sular appearing as a membranous sac wholly or partially inclosing 

 the joint, the funicular, here known as an interarticular ligament, 

 occupying the interior, and thus securing the union of the several 

 bones more firmly and effectively than would be possible for the cap- 

 sular ligament unassisted. 



The universal need which pertains to all mechanical contrivances 

 of motion has not been forgotten while providing for the perfect 

 working of the interesting piece of living machinery which performs 

 the function of locomotion, as we are contemplating it, and nature 

 has consequently provided for obviating the evils of attrition and 

 friction and insuring the easy play and smooth movement of its 

 parts by the establishment of the secretion of the synovia, the vital 

 lubricant of which we have before spoken, as a yellow, oil}'', or rather 

 glairy secretion, which performs the indispensable office of facili- 

 tating the play of the tendons over the joints and certain given 

 points of the bones. This fluid is deposited in a containing sac, the 

 lining (serous) membrane of which forms the secreting organ. This 

 membrane is of an excessively sensitive nature, and while it lines 

 the inner face of the ligaments, both capsular and fascicular, it is 

 attached only upon the edges of the bones, without extending upon 

 their length, or between the layers of cartilage which lie between 

 the bones and their articular surfaces. 



Our object in thus partially and concisely reviewing the structure 

 and condition of the essential organs of locomotion has been rather 

 to outline a sketch which may seiwe as a reference chart of the gen- 

 eral features of the subject than to offer a minute description of the 

 parts referred to. Other points of interest will receive proper atten- 



