142 Anatomy of Skeleton 



the cotyloid fossa and transverse ligament : it is (p. 127) the remains of the primitive 

 capsule isolated by the secondary taking up of the pubic surface into the joint, and 

 has little mechanical value, but carries some small vessels and nerves to the head of 

 the bone. 



The construction of this joint can be contrasted with that of the shoulder. In 

 both there is power of movement in any direction, although the range of movement 

 is much less in the hips. In the shoulder the freedom of movement is obtained by 

 sacrificing the strength of a supporting bony articulation, but security of the joint 

 is nevertheless well attained by the muscles inserted close to the articular surface, which 

 again is made possible by the existence of such an insecure articulation. On the other 

 hand, the strength of the joint by bony support is a paramount necessity in the hip, and 

 hence a deep articulation with consequent limitation of movement ; but the range 

 of movement and power of muscles is increased by lengthening the neck, a modification 

 that would be impossible in the shoulder. 



The Ilio-femoral ligament is tight when the upright position is assumed, and thus 

 dispenses with the necessity for muscular effort in sustaining the attitude. This would 

 be necessary otherwise, for the line of incidence of the centre of gravity of the upright 

 trunk passes through the back part of the joint and would tend to bend the body back 

 on the hip. The ligament is said to be proportionately shorter in women, a fact asso- 

 ciated with the greater obliquity of the pelvis and convexity of the lumbar column, 

 but it appears doubtful whether these last-named characters should be related with the 

 shortness of the ligament as cause or as effect. An effect of the shortness is certainly 

 seen in the inability of a woman to extend her thigh on her pelvis further back 

 than what is practically the upright straight line, so that the pelvis has to swing 

 back on that side when more than short strides are taken ; the effect is well seen 

 in the present-day combination of short and loose skirts with long striding, and 

 may be popularly expressed by saying that a man walks from his hips, a woman 

 from her lumbar region. 



Head. 



This has a separate epiphysis, and the epiphysial line practically but not abso- 

 lutely corresponds with the edge of the articular surface. A prolongation of the 

 cartilage-covered surface on to the front of the neck is frequently found : this underlies 

 the Ilio-psoas tendon. 



The head forms about two-thirds of a sphere, and is larger in male than in female 

 bones. The position and size of the fovea varies : one or two small foramina sometimes 

 seen in it are for vessels derived from the obturator artery. The synovial funnel that 

 surrounds them is attached to the depressed margin of the fovea and is lost outside this 

 on the cartilage. 



The Neck (Figs. 117 and 118). 



The neck is really a prolongation of the shaft, in its development and ossification 

 and in its structure. At birth (Fig. 116) the neck is short and thick and ossified by the 

 extension upwards of the shaft ossification, capped by the cartilaginous head. As 

 development proceeds the neck is gradually elongated, still carrying the epiphysis of 

 the head as a cap on its extremity. The angle it forms with the shaft varies with the 

 extent of its growth, being more open in the young bones and decreasing as growth 

 proceeds, but not after full growth is attained. In the adult the angle is as a rule 

 about 1 20 degrees, but may vary between no degrees and 140 degrees : it is smaller 

 in women than in men and in short than in long bones. Modification of the angle is 



