428 



ZOOLOGY 



SECT.. 



The pelvic arch (Fig. 1022) contains the same elements as in 

 the Pigeon, but the union of the ilium with the sacrum is less 



intimate, the acetabulum is not 

 perforated, and the pubes of 

 opposite sides unite ventrally in 

 a symphysis (s?/.). The three 

 bones of the pelvis, ilium, pubis 

 and ischium, are separate ossifi- 

 cations in the young Rabbit : 

 but in an adult animal complete 

 fusion takes place between the 

 bones. The ilium and ischium 

 meet in the acetabulum or arti- 

 cular cavity, which they contri- 



^^ \V /'"H P k u ^ e * * orm ^ r ^ e head of 



r ) J y jjrjr**^ the femur, but the remainder 



[ \ T| JLz>tf of the cavity is bounded, not by 



*s ;il. \J i the pubis, but by a small inter- 



calated ossification the cotyloid 

 bone. The ilium (il.) has a 

 rough surface for articulation 

 with the sacrum. Between the 

 pubis (pub.) in front and the 

 ischium (isch.) behind is a large 

 aperture the obturator fora- 

 men (obt.). The femur is rotated 

 forwards when compared with that of the Lizard, so that the limb is 

 nearly in the same plane as the fore-limb, and the pre-axial border is 

 internal and the originally dorsal surface anterior. The femur has 

 at its proximal end a prominent head for articulation with the aceta- 

 bulum, external to this a prominent process the great trochanter. 

 and internally a much smaller the lesser trochanter, while a small 

 process or third trochanter is situated on the outer border a little 

 below the great trochanter. At its distal end are two prominences 

 or condyles, with a depression between them. Two small sesa- 

 moids or fabellce are situated opposite the distal end on its 

 posterior aspect; and opposite the knee-joint, or articulation 

 between the femur and the tibia, is a larger bone of similar- 

 character the patella. The tibia has at its proximal end two 

 articular surfaces for the condyles of the femur; distally it has 

 also two articular surfaces, one, internal, for the astragalus, the 

 other for the calcaneum. The fibula is a slender bone which 

 becomes completely fused distally with the tibia. 



The tarsus (Fig. 1023) consists of six bones of irregular shape, 

 arranged in two rows, one of the bones the navicular (nav.) 

 being intercalated between the two rows. In the proximal row are 

 two bones the astragalus (ast.) and the calcaneum (cal.) both 

 articulating with the tibia ; the calcaneum presents behind a long 



FIG. 1022. Xiepus cuniculus. Innominate 

 bones and sacrum, ventral aspect, acet. 

 acetabulum ; il. ilium ; isch. ischium ; obt 

 obturator foramen ; pub, pubis ; sacr. 

 sacrum ; sy. symphysis. 



