164 ANATOMY OF THE WOOD RAT 



Distad of the great trochanter the lateral ridge rises to 

 form the lateral crest, or third trochanter of the femur. The 

 cranial surface of this is slightly concave, to an individually 

 differing degree, and as might be expected, the crest is 

 relatively less developed in young animals. There is much 

 individual, but practically no subgeneric variation. Upon 

 both borders of the crest proper and for some distance upon 

 either ridge adjoining is inserted the adductor brevis, and 

 immediately caudad, the gluteus superficiahs posterior. 

 Distad, in line with the crest for haK the length of the shaft, 

 is inserted the adductor magnus. 



The femur ends distad in two condyles separated craniad 

 by the trochlea for the reception of the patella, and caudad 

 by the intercondyloid fossa. Upon the lateral epicondyle 

 there may usually be descried three slight fossa — the disto- 

 caudal one for the origin of the pophteus; the disto-cranial 

 for the insertion of the extensor digitorum longus; and the 

 more proximal for the attachment of the external collateral 

 ligament. A corresponding fossa upon the medial epicondyle 

 is for the attachment of the internal collateral ligament. 

 There is a caudal angle to each condyle, within which is 

 situated the lateral and medial sesamoid bones respectively. 

 They are really invested in the heads of the gastrocnemii 

 lateralis and medialis. In addition there are two smaller, 

 anterior sesamoids, invested in the semilunar cartilages 

 of the knee joint and situated one at the ental margin of 

 either condyle, between the femur and tibia. 



The only remaining muscle having attachment upon the 

 femur is the plantaris, which arises from the tissue adjoining 

 the lateral sesamoid, and to a slight extent from the lateral 

 epicondyle itself. 



Lower leg 



Patella. Although a distinct bone, the patella or knee cap 

 is analogous to the olecranon of the fore limb. It is about 13 



