ACETABULUM. 169 



tained viscera of the pelvis by the actions of the internal ; nor 

 of the external being bruised by the thigh bone, especially by 

 its lesser trochanter, in the motions of the thigh inwards : both 

 which inconveniences must have happened, had the ossa innoin- 

 inata been complete here, and of sufficient thickness and 

 strength, as the fixed point of these muscles. 



The bowels sometimes make their way through the notch 

 for the vessels at the upper part of this thyroid hole ; and this 

 causes a hernia at this place. 



The acetabulum is situated near the outside of the great 

 foramen. The margin of this cavity is very high, and is siill 

 much more enlarged by the ligamentous cartilage, with which 

 it is tipped in a recent subject ; round the base of this margin 

 the bone is rough and unequal, where the capsular ligament of 

 the articulation is fixed. At the upper and back part of the 

 acetabulum the margin is much larger and higher than any 

 where else ; which is very necessary to prevent the head of the 

 femur from slipping out of its cavity at this place, where the 

 whole weight of the body bears upon it, and consequently 

 might otherwise thrust it out. As the margin is extended 

 downwards and forwards, it becomes less ; and, at the internal 

 lower part, is a deficiency in it ; from the one side of which to 

 the other, a ligament is placed in the recent subject, under 

 which a large hole is left. Besides this difference in the height 

 of the margin, the acetabulum is otherwise unequal ; for the 

 lower internal part of it is depressed beJow the cartilaginous 

 surface of the upper part, and is not covered with cartilage; 

 into the upper part of this particular depression, where it is 

 deepest, and of a semilunar form, the ligament of the thigh 

 bone, commonly, though improperly called the round one, is 

 inserted : while, in its more superficial lower part, a mass of 

 adipose matter is lodged. The greatest part of this separate 

 depression is formed in the os ischium. 



The ossa innominati are joined, at their back part, to each 



side of the os sacrum, by a sort of suture, with a very thin 



intervening cartilage, which serves to cement these bones 



together : and strong ligaments go from the circumference of 



15 



