380 



ZOOLOGY 



SECT. 



FIO. 1046. coiumba livia. 



Left manus of a nestling. The 

 cartilaginous parts are dotted. 



size. As usual it furnishes the dorsal portion of the acetabulum, 

 and on the posterior edge of that cavity is produced into a process, 

 the anti-trochanter (a.tr.), which works against the trochanter, a 



process of the femur. The ventral portion 

 of the acetabulum is furnished in about 

 equal proportions by the pubis and 

 ischium (Fig. 1047) : it is not completely 

 closed by bone, but is perforated by an 

 aperture covered by membrane in the 

 recent state. Both pubis and ischium are 

 directed sharply backwards from their 

 dorsal or acetabular ends. The ischium 

 (is.) is a broad bone, ankylosed posteriorly 

 with the ilium, and separated from it in 

 front by an ischiatic foramen (Fig. 1038, 

 is. for. ; Fig. 1047, i.s.f.). The pubis (pu.) 

 is a slender, curved rod, parallel with the 

 ventral edge of the ischium, and sepa- 

 rated from it by an obturator notch (Fig. 

 1038, obt.n. ; Fig. 1047, ob.f.). Neither 

 ischium nor pubis unites ventrally with 

 i, phalanx _o'f first digit ; ph. 2, its fellow to form a symphysis. 



In the hind-limb the femur (Fig. 1048, 

 fe.) is a comparatively short bone. Its 

 proximal extremity bears a prominent 

 trochanter (tr.) and a rounded head (hd.), the axis of which is at 

 right angles to the shaft of the bone ; so that the femur, and 

 indeed the whole limb, lies in a plane parallel with the sagittal 

 plane of the trunk, and is not directed outwards as in Reptiles. 

 Its distal end is produced 

 into pulley-like condyles. 

 There is a small sesa- 

 moid bone (i.e., a bone 

 developed in a tendon), 

 the patella (pat.), on the 

 extensor side of the knee- 

 joint. Articulating with 

 the femur is a very long 

 bone, the tibio-tarsus 

 (ti.ts.), produced on the 

 anterior face of its proxi- 

 mal end into a large 

 cnemial process (cn.pr.) for 

 the insertion of the extensor muscle of the thigh. Its proximal 

 articular surface is slightly' hollowed for the condyle of the femur ; 

 its distal end is pulley-like, not concave like the corresponding 

 extremity of the tibia of other Amniota. The study of develop- 



pu 



FIG. 1047. Coiumba livia. Left innominate of a 

 nestling. The cartilage is dotted, ac. acetabulum ; 

 a. tr. anti-trochanter; il. pre-acetabular, and il' . post- 

 acetabular portion of ilium ; is. ischium ; t. s. f. 

 ischiadic foramen ; ob. f. obturator notch ; pu. pubis. 

 (From Parker's Zootomy.) 



