168 



EXTREMITY. 



tact with the articular surfaces of the vertical 

 tibitE. In women, in consequence of the more 

 horizontal position of the neck of the femur 

 and the greater width of the pelvis, the ob- 

 liquity is more manifest, and hence they are 

 naturally more in-kneed than men, as from 

 the greater projection of the internal condyle 

 that surface alone would come in contact 

 with the tibia if the position of the femur 

 were vertical. The separation above is ef- 

 fected by the neck of the bone, and the ad- 

 vantage of this arrangement is to give a more 

 favourable insertion to the muscles of rotation ; 

 they thus acquire a lever power proportionate 

 to the length of the neck, a fact which is 

 abundantly manifest by comparing the relative 

 powers of rotation in the shoulder and hip 

 joints; in the former these motions are more 

 extensive, because, from the peculiar form of 

 the joint, the obstacles to extent of motion are 

 fewer; in the latter they are effected with greater 

 power at a less expense of muscular force. 



In comparing the femur of man with that of 

 the lower mammalia, we notice the imperfect 

 developement or the non-developement of the 

 cervix in the latter, the head in some being 

 placed nearly vertically over the shaft of the bone, 

 and also the small size of the trochanters, and 

 the magnitude of the trochanter major in some 

 classes. The curved form of the shaft of the 

 femur is much less in the lower mammalia 

 than in man; in some the femur is perfectly 

 straight, and as a consequence the linea aspera 

 or spine is indistinctly marked. The propor- 

 tionate length of the femur to the other bones 

 of the inferior extremity differs also : in man 

 it exceeds that of the tibia; in the inferior 

 mammalia, although in most cases the strongest 

 bone, the femur is shorter than the tibia, and 

 shorter even than the foot, although longer 

 than each segment of this portion of the limb. 

 The trochlea in the inferior extremity is deeper, 

 and the transverse dimensions of the condyles 

 are less than in man. 



Patella, (rotula, knee-pan, os sesamoideum 

 maximum, Berlin ; Fr. la rotule; Germ, die 

 Knicscheibe). This bone, although belonging 

 to the class of sesamoid bones, is yet so fully 

 developed in the adult human subject, and is 

 so essential to the integrity of the knee-joint, that 

 it is usual to examine its anatomical characters 

 along with those of the other bones of the in- 

 ferior extremity. Its developement in the tendon 

 of the rectus femoris leads to its being classed 

 among the sesamoid bones. 



The patella is of a triangular form, the apex 

 being directed downwards and the base up- 

 wards; the former is connected with the tibia 

 by the continued tendon of the rectus, under 

 the name of ligamentum patella;; the tendon 

 of the rectus and the tendinous expansions of 

 the triceps extensor are inserted into the base, 

 which expansions are likewise implanted into 

 the margins of the bone, so that the whole 

 circumference and anterior surface of the pa- 

 tella are invested with tendinous fibres. 



The anterior surface of the patella is very 

 slightly convex, and exhibits a fibrous ap- 

 pearance produced by vertical and parallel 



fibres, with narrow fissures between, into 

 which the fibrous expansion which invests this 

 surface is implanted. The posterior surface 

 is articular and adapted to the trochlea of 

 the femur. A vertical ridge, which inclines a 

 little outwards in its descent, divides this sur- 

 face into two lateral portions ; each of these por- 

 tions is a concave articular facet for adaptation 

 to the anterior part of each condyle of the 

 femur, and consequently there is between these 

 surfaces the same inequality which exists be- 

 tween the condyles. In the recent condition 

 these surfaces are covered by a soft and very 

 elastic cartilage. 



Structure and developement. The patella 

 is entirely composed of cancellated texture, 

 the anterior surface being covered by a thin 

 lamella of very fibrous compact tissue already 

 referred to. This bone is developed by a single 

 point of ossification, which commences about 

 the second year. 



The patella exists pretty generally among 

 Mammalia, also among Birds. It is most de- 

 veloped in the Pachydermata and the Solipeds, 

 and also in the Monotremata ; and least so in 

 the Carnivora and Quadrumana. It is absent in 

 Cheiroptera and Marsupiata.* 



Leg. The bones that form the second 

 segment of the inferior extremity are the 

 Tibia and Fibula. 



Tibia, (shin-bone; Germ, das Schienbein.) 

 This bone is situated between the inferior ex- 

 tremity of the femur and the astragalus. Its 

 length is to that of the femur as five to six. 

 It forms the principal support of the leg, on 

 the inside of which it is placed, and its volume 

 is five times that of the fibula. After the 

 femur, it is the longest bone in the body, being 

 longer than the humerus. 



The upper or femoral extremity of the tibia 

 is thicker and broader than the remaining parts 

 of the bone, and is properly the head of the 

 bone. Its transverse extent is much greater 

 than its antero-posterior. Its superior surface 

 presents two bony processes lying on the same 

 plane, denominated condyles of the tibia. 

 Each of these has upon its superior surface a 

 superficial concave articular facet, oval with long 

 axis from before backwards; to these surfaces 

 the term condyle has been improperly applied ; 

 but they are more correctly called the glenoid 

 cavities of the tibia, (cavitatcs glenoidete, ex- 

 terna et interna). These cavities correspond 

 to the condyles of the femur, having the semi- 

 lunar cartilages interposed ; the outer cavity 

 approaches more to the circular form than the 

 internal one; it is likewise much less deep, 

 and at its posterior part it is even convex. 

 The internal one, on the other hand, is 

 uniformly concave, and its antero-posterior 

 axis greatly exceeds its transverse. These sur- 

 faces are separated in the centre by a pyra- 

 midal eminence whose apex appears bifurcated, 

 the subdivisions of which are separated by a 

 narrow rough space. This is the spine of the 

 tibia, (acclivitas intercondi/lmdea ) ; it corres- 

 ponds to the intercondyloid fossa of the femur 



* Meckcl, Anat. Compar. 



