OSTEOLOGY AND ARTHROLOGY 83 



towards the middle line, but without joining the pubis of 

 the opposite side. On this account there is no symphysis 

 pubis in birds. Nevertheless, an exception must be noted 

 in the case of the ostrich, the pubic bones of which meet in 

 the middle line, and are articulated in form of a symphysis. 



The Thigh 



A single bone, the femur, forms the skeleton of this 

 portion of the lower limb. 



The Femur. — The bone of the thigh is, in man, directed 

 downwards and inwards ; this obliquity, we may remind 

 the reader, is due to the difference in length of the two 

 condyles which form its inferior extremity ; the internal 

 is the more prominent, the result of which is that when 

 the femur is held vertically, the internal condyle descends 

 lower than the external. Now, as those two articular 

 expansions rest on the horizontal plane formed by the upper 

 extremity of the tibia, it follows that the superior part of 

 the femur inclines towards the side of the shorter con- 

 dyle — that is to say, outwards — and that, the leg being 

 vertical, it and the bone of the thigh unite in forming an 

 angle, of which the apex is directed towards the inner side 

 of the knee. 



In many mammals the two condyles are equally pro- 

 minent, the result of which is that the femur inclines neither 

 inwards nor outwards, but is contained in a plane parallel 

 to the axis of the trunk ; while the leg is included in the 

 same plane. Nevertheless, although contained in the 

 plane which we have just indicated, the femur is obliquely 

 placed, and directed downwards and forwards ; it accord- 

 ingly forms, with the pelvis, an angle, of which the opening 

 is directed to the anterior aspect of the body. 



In reptiles and in birds the femur and leg are both placed 

 in the same plane, but this plane is not parallel to the 

 axis of the trunk. This is the result, on the one hand, of 

 the thorax being wide, and, on the other hand, of the femur, 

 which is directed forwards, being in contact by its anterior 

 extremity with the lateral aspect of the costal region, it is 



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