312 



ZOOLOGY 



SECT. 



to the distal epiphysis of the ulna on its post-axial side. The first 

 digit or pollex consists of a metacarpal and two phalanges, the 

 second of a metacarpal and three phalanges, the third of a meta- 

 carpal and four phalanges, the fourth of a metacarpal and five 

 phalanges, and the fifth of a metacarpal and three phalanges. 

 The number of phalanges in the first four digits is, therefore, one 

 more than the serial number of the digit. 



The pelvic arch (Fig. 976) consists of two triradiate bones, the 

 ossa innominata, each ray being a separate bone. On the outer side 

 at the point from which the rays diverge is a concave articular 

 surface the acetabulum (Ac) for the head of the femur. From 

 the region of the acetabulum one of the rays, the ilium (I), a com- 

 pressed rod, passes upwards and backwards to articulate with 



the sacral region of 

 the spinal column. 

 A second ray the 

 pubis (p) - - passes 

 downwards and for- 

 wards to meet its 

 fellow in the middle 

 line, the' articula- 

 tion being termed 

 the pubic symphysis. 

 In the middle line 

 in front, between 

 the anterior ends of 

 the pubes, is a 

 small nodule of 

 calcified cartilage, 

 epipubis (Cep). 

 third ray or 

 ischium (Is) runs 

 downwards and 

 backwards, and articulates with its fellow in the ischiatic symphysis, 

 the ventral ends of the two bones being separated by a plate of calci- 

 fied cartilage (S. Is). Between the pubes and ischia is a wide space, 

 the obturator foramen, divided by a median ligament (Ig) into a pair 

 of apertures, and a smaller aperture in each pubis (Fo') transmits 

 the obturator nerve. A small rod of bone, the os cloacce, or hypo- 

 ischium (Hp. Is), passes backwards from the ischiatic symphysis 

 and supports the ventral wall of the cloaca. 



The hind-limb consists, like the fore-limb, of three divisions ; 

 these are termed respectively the proximal or femur, the middle 

 or crus, and the distal or pes. The proximal division consists 

 of one bone, the femur ; the middle division of two, the tibia and 

 fibula ; the distal of the tarsal and metatarsal bones and the 

 phalanges. When the limb is extended at right angles with the 



FIG. 976. Pelvis of Lacerta vivipara, from the ventral side. 

 Ac. acetabulum ; Cep. epipubis. Fo'. foramen for obturator 

 nerve ; Hp. Is. hypoischium ; /. ilium ; 1 1, process representing 

 the pre-acetabular part of the ilium ; Lg. ligament ; In. 

 ischium ; p. pubis ; pp. prepubis ; S. Is. ischiatic symphysis. 

 (From Wiedersheim's Comparative Anatomy.) 



