302 DISEASES OF THE HORSE, 
form, being in one case comparatively 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, oily, 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 ee been rather 
to outline a sketch which may serve 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- 
