THE ERECT POSITION IN MAN. 227 



confer the peculiar grace and expression of its movements. 

 Progression in the human body costs less labour than in the 

 animal. All man has to do is to bend his body forward, and 

 then bring his pelvis forward by muscular action, the exertion 

 requisite to do which is determined by the peculiar pendulum- 

 like movements of the lower limbs. 



5. — The Haunch. 



a. The shafts of the human iliac bones are short and 

 massive ; and the direction of their axes is altogether peculiar. 

 They are vertical, and in front of the line of gravity. In the 

 animal they are elongated, oblique from above downwards 

 and backwards, and in addition are situated behind the line 

 of gravity. The axis of the human ilium is very important, 

 because the weight of the trunk is borne upon it. 



b. There are five parts in the haunch-bone of the mammal 

 — viz. the sacral articular facet, the pubic symphysis, the 

 ischial tuber, the anterior superior spine of ilium and the 

 acetabulum, which, considered in regard to their relative 

 positions, are quite peculiar in man. The line joining the 

 sacral articular facet, and the acetabulum, is the axis of the 

 iliac bones ; the remaining three points form the angles of a 

 nearly equilateral triangle, to winch and to the sides and sur- 

 faces of the triangles, the muscles which balance the trunk 

 on the thigh-bone are attached. The sartorius, gracilis, and 

 semi-tendinosus, are the three muscles winch are connected to 

 the angles of this triangle, muscles which are of great import- 

 ance in balancing the body when standing on one leg. The 

 human haunch-bone is the only form of haunch-bone adapted 

 foi the erect position. It is a lever of which the hip-joint 

 is the fulcrum, the sacral facet representing the extremity of 

 the arm for the resistance, the pubic symphysis, the ischial 

 tuber, and the anterior superior pi E the ilium, the extremi- 

 ties respectively of three arms for the power. 



