54 THE SURGICAL ANATOMY OF THE HORSE 



convex in all directions, and in the articulated joint is accommodated in 

 the cotyloid cavity of the innominate bone. It is not entirely articular 

 however, for it presents inwardly a deep triangular, non-articular, 

 roughened area termed the sulcus, the apex of which extends towards 

 the centre of the head for a distance which is about two-thirds the 

 radius of the articular surface. The base of the sulcus is represented by 

 an arc of the circumference removed. The sulcus gives insertion to the 

 pubio-femoral and round ligaments of the hip joint. The smooth articular 

 surface of the head is surrounded by a roughened line which is continued, 

 but more faintly marked, across the base of the sulcus. To this roughened 

 Une the capsular ligament of the hip joint is attached. Below this Hne 

 the head is almost completely encircled by a well-marked constriction 

 termed the neck. The neck however is ill-defined outwardly where the 

 surface of the head has, in the dried bone, but a faint line of demarca- 

 tion between it and the non-articular area which extends to the great 

 trochanter. This latter area is slightly concave from side to side, but from 

 before backwards it presents a slight degree of convexity. Anteriorly it 

 extends on to the inner surface of the convexity, whilst posteriorly it 

 passes on to the inner surface of the summit. Near the convexity this 

 area presents a large number of foramina, some of which are of con- 

 siderable size. They transmit blood vessels into the cancellated tissue of 

 the bone. 



The lower extremity of the femur is made up of the trochlea, two 

 condyles, and an intercondyloid groove. The trochlea is placed anteriorly 

 and consists of a vertical articular groove bounded by two parallel ridges 

 termed the lips. The articular area extends on to the concentric surface 

 of each ridge. The inner lip is much the more prominent, and at its 

 superior extremity it presents a well-marked enlargement which projects 

 forwards and which terminates abruptly, a point which is of consider- 

 able importance in dealing with luxation of the patella. The anterior 

 border of the outer ridge is sharp and well defined, as distinguished from 

 that of the inner ridge, which is blunt. This border of the outer ridge 



