10 Proceedings of the Royal Physical Society. 



with the so-called adductor tubercle of the inner condyle of 

 the femur, while the continuation of the original tendon now 

 plays the part of the internal lateral ligament of the knee- 

 joint. On the other hand, the Adductor group has become 

 likewise reduced in numbers, as well as considerably modi- 

 fied in its attachments. Thus, in man an adductor minimus 

 muscle distinct from the adductor magnus is rare. It is also 

 extremely rare to find the adductor magnus inserted into the 

 popliteal surface of the femur, whereas among apes, e.g., the 

 chimpanzee, this area of the femur is not devoid of a clothing 

 of muscle, but is covered by the adductor magnus close down 

 to the posterior ligament of the knee-joint. In the popliteal 

 space, the persistence of the obturator nerve, which supplies 

 this part of the adductor magnus muscle, and its occasional 

 association as an articular nerve for the knee-joint, indicates 

 that, while the muscle has receded, the nerve has persisted in 

 its original position. It is highly probable that the convexity, 

 which very occasionally characterises the popliteal surface of 

 the femur of man, may be due to such a reverted condition 

 of the adductor magnus muscle. The Extensor group of 

 thigh muscles presents certain most pronounced evolutions. 

 Two of its members, viz., the vastus externus and vastus 

 internus, are believed to be responsible for the production of 

 that essentially human feature, the linea aspera. This feature 

 is not, in the correct sense of the term, a line, but rather a 

 narrow raised area, of the nature of a flattened ridge, project- 

 ing backwards from the shaft of the femur, particularly in its 

 middle third. Manouvrier has named this ridge t\i.Q pilastre, 

 and this name admits of comparison being made between this 

 area in men and other mammals. It is only in man that it 

 assumes the form of a narrow, almost linear, area ; in other 

 mammals it forms a surface of considerable width, without 

 any attempt at the formation of a crest projecting backwards. 

 The vasti muscles are believed to produce this crest through 

 their action in connection with the extension of the knee- 

 joint in the act of walking erect, or it may be in connection 

 with raising the body from the squatting attitude, since the 

 linea aspera finds its most exaggerated development among 

 the aboriginal Australians, and nut among modern civilised 



