xvin.] GENERAL CHARACTERS. 329 



notch (intercondylar) into two prominent rounded eminences, 

 called condyles (Fig. 117, ec and ic\ The slightly elevated 

 roughed portions of bone above the articular condyles are 

 termed the tuberosities. 



The femur has a main centre of ossification for the shaft, 

 and epiphysial centres for the head, for each trochanter, and 

 for the lower extremity. (See Fig. 117.) In most Mammals 

 the great trochanter and head coalesce together before they 

 join the shaft. The lower epiphysis is the last to become 

 united. 



The skeleton of the second segment of the limb consists 

 of two bones, the tibia and fibula?- of which the former is 

 the larger in all Mammals. These bones always lie in their 

 primitive, unmodified position, parallel to each other, the 

 tibia on the pre-axial, and the fibula on the post-axial side 

 and are never either permanently crossed or capable of any 

 considerable amount of rotation, as in the corresponding 

 bones of the fore-limb. In the ordinary walking position the 

 tibia is internal, and the fibula external. 



The tibia has an expanded proximal end, with a flattened 

 articular surface, divided into two slightly concave facets, by 

 a rough median eminence, to which the intra-articular or 

 crucial ligaments of the knee-joint are attached. The shaft 

 is usually more or less trihedral, with one flat surface directed 

 backwards, and one border forwards. The upper end of 

 this border is thickened into a rough tuberosity, into which 

 the tendon of the great extensor muscles of the leg are 

 inserted. The lower end is slightly expanded, and has a 

 somewhat square articular surface to receive the proximal 

 bone of the tarsus, or astragalus. The inner (pre-axial) side 

 of- the bone is prolonged beyond this surface, forming a 



1 Also occasionally called perone, whence " peroneal," applied to 

 structures in relation with it. 



