OS FEMORIS. 203 



y rotary motion of the thigh, have occasioned the name of trochan- 

 ters to be given to these processes. 



The body of the os femoris is convex on the forepart and 

 concave behind, which enables us to sit without leaning too 

 much on the posterior muscles. 



On the posterior concave surface is a broad rough ridge called 

 lima aspera, which commences near the great trochanter, and 

 continues downwards, more than two-thirds of the length of 

 the bone, when it divides into two ridges, which descend 

 towards each condyle. The internal of these ridges is the most 

 smooth, and the space between them is nearly flat. Near the 

 end of each of these ridges, a small, smooth-protuberance may 

 often be remarked, where the two heads of the external gastroc- 

 nemius muscles take their rise ; and from the forepart of the 

 internal tubercle, a strong ligament is extended to the inside of 

 the tibia. 



The lower end of the os femoris is larger than any other part 

 of it, and is formed into two great protuberances, one on each 

 side, which are called its condyles : between them a considerable 

 cavity is found, especially at the back part, in which the crural 

 vessels and nerves lie. The internal condyle is longer than the 

 external, which must happen from the oblique position of this 

 bone, to give less obliquity to the leg. These processes are of 

 an oblong form, and are placed obliquely with respect to each 

 other ; being in contact before and separated to a considerable 

 distance behind. 



They form in front a smooth pulley-like surface, the external 

 side of which is highest, on which the patella moves. 



Below, they are flat ; and posteriorly, they are regularly 

 convex. 



Between these convex portions is a rough cavity, from which 

 the crucial ligament arises, to be attached to the tibia. Round 

 the lower end of the thigh bone, large holes are found, into 

 which the ligaments for the security of the joint are fixed, and 

 blood-vessels pass to the internal substance of the bone. 



The thigh bone being articulated above with the acetabulum 

 of the os innominatum, which affords its round head a secure 

 and extensive play, can be moved to every side : but it is 



