THE CURVATURES OF THE ARTICULAR SURFACES, ETC. 509 



to trace this cusp to a ridge extending across from the neck 

 of the bone to the fossa, dividing the surface into an anterior 

 and posterior area. If the eye be carried along two series of 

 lines diverging from the upper angles of the fossa, the one 

 series outwards and forwards on the anterior area, and the 

 other outwards and backwards on the posterior area, and with 

 a convexity on each line towards the ridge corresponding to 

 the curvature of that part of the surface on which it is traced, 

 each series will be found to close with the anterior and 

 posterior margins of the fossa for the ligamentum teres. It 

 will also be observed why the transverse lines of curvature 

 increase in rapidity from above downwards. 



The cartilaginous surface of the acetabulum consists of 

 three areas situated respectively on the pubic, iliac, and 

 ischial portions of the cavity. They are more or less dis- 

 tinctly separated in the dry or recent bone by depressed lines. 

 The marginal terminations of these lines are indicated at the 

 brirn of the cavity by the three notch-like hollows of the edge, 

 that between the ischial and iliac at the middle of the 

 posterior margin ; that between the iliac and the pubic on 

 the upper margin at the outer side of the ilio-pectineal 

 eminence ; that between the pubic and ischial by the fossa 

 and notch of the lower part and margin of the cavity. These 

 three notches, with the three intermediate wave-like projec- 

 tions, produce an undulating form of margin in the macerated 

 bone. The three projections are respectively formed by the 

 upper part of the iliac, the lower part of the ischial, and the 

 anterior part of the pubic portion. The margin of the arti- 

 cular surface on the head of the femur is also undulating. 

 It sweeps outwards opposite the front and back of the great 

 trochanter, and slightly below opposite the lesser trochanter, 

 and therefore recedes inwards opposite the upper margin of 

 the great trochanter, also before and behind the ridge which 

 connects the head to the small trochanter. In the erect 



