EXTREMITY. 



165 



animals, evidence of the existence of these 

 motions is afforded by certain points in the 

 conformation of the radius and ulna them- 

 selves, such as the peculiar form of the head 

 of the radius, and the concave articular sur- 

 face on the ulnar side of its lower extremity, 

 as well as the lesser sigmoid cavity of the 

 ulna, and the convexity on the radial side of the 

 head of the same bone. This is found in many 

 of the Carnivora, but chiefly in the Quadru- 

 mana. 



In the Ruminants and Solipeds the radius 

 and ulna are consolidated together so as to 

 form one bone ; they can, however, be distin- 

 guished at the humeral end, where the latter 

 bone is conspicuous by its elongated olecranon, 

 which not only affords insertion to the extensor 

 muscles of the arm, but also increases the secu- 

 rity of the elbow-joint. The radius, which is 

 the principal bone of the fore-arm, is so arti- 

 culated with the humerus as to admit of free 

 flexion and extension, but it is fixed in the 

 state of pronation. In many of the other Mam- 

 malia the radius and ulna are distinct through- 

 out, but do not admit of the rotation of the 

 one on the other ; this is the case in Rodentia, 

 many Carnivora, Pachydermata, Edentata, In- 

 sectivora, and Cetacea. In the Sloth, how- 

 ever, among the Edentata, the motions of pro- 

 nation and supination are conspicuous, and the 

 olecranon is imperfectly developed; on the 

 contrary, in the Edentata proper, as the Arma- 

 dillo, Megatherium, &c. these motions do not 

 exist, and the olecranon is very much deve- 

 loped. In the Cheiroptera the radius is the 

 principal bone of the fore-arm, the ulna being 

 developed only as to its humeral extremity 

 consisting sometimes of little more than its 

 olecranon ; and in some, as the Vespertilio vam- 

 pyrus, the olecranon exists in the form of a pa- 

 tella, connected with the upper extremity of 

 the ulna. 



In Birds the radius and ulna are distinct 

 throughout, but do not admit of motion between 

 them; they are fixed in a state intermediate be- 

 tween pronation and supination. 



The Hand. The third division of the upper 

 extremity is the hand : for the description of 

 the bones which compose it, we refer to the 

 article HASD. 



Inferior extremity. The bones which form 

 the skeleton of the inferior or pelvic extremity 

 are the femur, tibia, fibula, and the bones of 

 the foot, occupying subdivisions of this mem- 

 ber, which correspond to the arm, forearm, and 

 hand in the pectoral extremity. 



Femur (thigh-bone, os femoris v. cruris, os 

 coxa. Fr. os de la cuisse, le femur. Germ, das 

 Schenkelbein.) This is the largest and longest 

 bone of the skeleton ; it constitutes the upper part 

 of the inferior extremity, and is articulated with 

 the pelvis above and the tibia inferiorly. The 

 femur exhibits very obviously the characteristic 

 marks of the class of long bones in its elonga- 

 ted and cylindrical shaft, and its swollen extre- 

 mities. 



The superior extremity of the femur consists 

 of a spherical head, connected to the shaft of 

 the bone by a neck. The head is very regu- 



larly spheroidal, being nearly two-thirds of a 

 sphere ; it is limited towards the neck by a 

 waving line which passes all round, and corr- 

 sponds to the margin of the acetabulum. The 

 whole head of the femur is incrusted in the 

 recent state with articular cartilage, excepting 

 at one point, where there is a depression or pit, 

 varying in depth in different subjects. The 

 precise situation of this depression is just infe- 

 rior and posterior to the point at which the axis 

 of the head of the femur would pass out : into 

 this depression the ligamentum teres is in- 

 serted. 



From the head of the femur is prolonged 

 outwards and downwards to the upper end of 

 the shaft the neck (cervix v. collumfemoris). 

 This portion of bone, cylindrical where it is 

 connected to the head, gradually expands as it 

 proceeds outwards, and is flattened in front 

 and behind. That portion of the neck of 

 the femur which is connected with the shaft 

 may be called its base; here we observe two 

 lines, by which the demarcation between the 

 neck and shaft is indicated ; one of these lines 

 is anterior, being simply a rough line extending 

 from the great trochanter obliquely downwards, 

 inwards, and slightly backwards to the lesser 

 trochanter, and thence called the anterior inter- 

 trochanteric line, into which the capsular liga- 

 ment of the hip-joint is inserted ; the other line 

 may be more correctly designated a prominent 

 ridge ; it is situated at the posterior part of the 

 base of the neck, and extended also between the 

 trochanters, the posterior inter-trochanteric line. 

 The anterior surface of the neck of the femur is 

 for the most part plane, but slightly concave 

 just external to the line of junction of the head. 

 The superior surface of the neck is concave, 

 being limited on the outside by the great tro- 

 chanter ; the posterior surface is likewise con- 

 cave, being, as it were, hollowed from within 

 outwards. The inferior surface is slightly con- 

 cave from above downwards, but rounded from 

 before backwards : this surface inclines down- 

 wards and outwards, and at its termination is 

 connected with the trochanter minor behind, 

 and the inner side of the shaft of the bone in 

 front ; in length it exceeds all the rest ; the su- 

 perior surface is the shortest, and the posterior 

 is longer than the anterior. On all the surfaces 

 of the neck we observe numerous foramina for 

 the transmission of vessels into the substance 

 of the bone; these foramina are largest and 

 most numerous on the superior surface. 



At the superior angle of the base of the neck 

 of the femur, and at the upper and outer part 

 of the shaft of the bone, we observe a large and 

 thick process, the trochanter major, (from 

 T^Q^ctu, roto,) processus exterior femor is ; it is 

 a prolongation upwards of the shaft of the 

 bone, but its most elevated point is below the 

 level of the head of the bone, corresponding to 

 the upper part of the line of junction of the 

 head with the neck. " This eminence," says 

 Cruveilhier, " whose size is considerable, and 

 which makes a very manifest prominence under 

 the skin, ought to be studied with care in its 

 relations as to its relative position ; first, with 

 the crista ilii, beyond which it projects exter- 



