MAMMALS. 565 



is relatively shorter tlian in man, where it is the longest bone of the 

 skeleton, Tlie head of the thigh-bone is seated upon a short neck 

 "which leaves the bone at a right angle; from this part also the 

 external or great trochanter ascends above the head of the thigh- 

 bone. This bone is remarkably short in the seals (Phocce), where 

 the shaft almost disappears and the two articular extremities form 

 nearly the whole mass. Whilst in man the axis of the thigh-bone 

 in the erect position deviates little from that of the vertebral column, 

 the thigh-bones even of the apes are bent more forward and form an 

 obtuse angle with the pelvis; hence these animals always stand 

 with the knees bent. In the carnivorous animals the thigh-bone 

 makes nearly a right angle with the pelvis. In other mammals, as 

 in the horse and the ruminants, the angle becomes even acute. 



With the thigh-bone (femur) two other bones of the leg are 

 connected below, the tibia and thejihula. The knee-joint is strength- 

 ened by many ligaments, by the capsular ligament, by the crucial 

 ligaments, the lateral ligaments and the fibrous expansions of the 

 muscles. At its anterior surface is situated the patella, which 

 appears to be wanting in different marsupial animals only, is small 

 in the carnivores, broad in the horse and the pachyderms. It is 

 a round, flat, bony disc, which is attached by a ligament arising 

 from its inferior extremity to the projecting anterior surface of the 

 tibia. This ligament is of a tendinous nature and arises from the 

 tendinous tissue of the extensor muscles ^ The tihia corresponds 

 to the radius of the fore-arm, and is situated forward ; the fibula 

 corresponds to the ulna, and is situated backward and outward. The 

 tibia, however, can rotate round the fibula in some marsupiates only, 

 like the radius round the ulna in man and many mammals. In 

 various mammals the tibia and fibula have coalesced, mostly at the 

 lower part. In the horse the fibula is a long stile, which becomes 

 thin downwards and extends from the upper extremity of the tibia 

 to about one half of it only. In the ruminants, on the contrary, the 

 inferior extremity alone of the fibula is present. The tibia termi- 

 nates below with a smooth articular surface before the first tarsal 

 bone, and has on the inside a process Avhich extends downwards 

 (the inner ankle, malleolus intermis). The fibula forms with its 



1 Hence the patella is a large sesamoid bone, as Bichat and, before him, Bertin 

 had justly observed. 



