204 THE LEG. 



restrained in its motion outwards by the high brims of the 

 cavity, and by the round ligament ; for otherwise the head of 

 the bone would have been frequently thrust out at the breach of 

 the brims on the inside, which allows the thigh to move consider- 

 ably inwards. The body of this bone enjoys little or no 

 rotary motion, though the head most commonly moves round its 

 own axis ; because the oblique direction of the neck and head 

 from the bone, is such, that the rotary motion of the head can 

 only bring the body of .the bone forwards and backwards. Nor 

 is the head, as in the arm, ever capable of being brought to a 

 straight direction with its body ; so far, however, as the head can 

 move within the cavity backwards and forwards, the rest of the 

 bone may have a partial rotation. 



From the oblique position of these bones it results, that there 

 is a considerable distance between them above, while the knees 

 are almost contiguous. Sufficient space is thereby left for the 

 external parts of generation, for the two great outlets of urine 

 and faeces, and for the large thick muscles that move the thigh 

 inwards. At the same lime this situation of the thigh bone 

 renders our progression quicker, surer, straighter, and in less 

 room : for, had the knees been at a greater distance from each 

 other, we must have been obliged to describe some part of a 

 circle with the trunk of our body in making a long step ; and 

 when one leg was raised from the ground, our centre of gravity 

 would have been too far from the base of the other, and we 

 should consequently have been in danger of falling ; so that our 

 steps would neither have been straight nor firm, nor would it 

 have been possible to walk in a narrow path, had our thigh 

 bones been otherwise placed. In consequence, however, of the 

 weight of the body bearing so obliquely on the joint of the knee 

 by this situation of the thigh bones, weak rickety children 

 become knock-kneed. 



The Leg 



Is composed of the two bones, the TIBIA and FIBULA. 

 The patella being evidently appropriated to the knee-joint, 

 may be regarded as common both to the thigh and leg. 



