THE PELVIC GIRDLE. 47 



already been g-iven. This bone also presents differences in the two 

 sexes. MeckeFs^ observation that it exists only in the male is 

 incorrect; it is a large, broad and sickle-shaped mass o£ calcified 

 cartilage or even true bone, while in the female it is simply a small 

 cartilaginous rod ; as this almost entirely disappears in dried speci- 

 mens, Meckel^s statement is explained. The second, fing-er has in 

 the frog" assumed the functions of the thumb, and, in the males, in 

 the breeding" season swells and underg-oes an essential alteration of 

 structure. The metacarpal of this finger also displays differences 

 in the sexes, being" in the male stronger, broader, and on the inner 

 side provided with a spine-like prolongation, for the tendon of the 

 abductor digiti II [poUicis) longus, which attains an unusual de- 

 velopment during the breeding- season. The remaining- metacarpal 

 bones, the third, fourth, and fifth, are of similar form, the last 

 being" provided with a tubercle. The anterior articular extremities 

 are rather broad and concave, and the posterior have rounded 

 heads. 



c. The ^'haAasL^Q^, phalanges dlgitorum. The hand has fourfing-ers 

 and the rudiment of a fifth, which latter is completely hidden under 

 the skin, and as already explained, consists of a metacarj^al only. 

 Of the four fingers, the fourth is the long-est, the third the shortest, 

 the second and fifth of intermediate and about equal length; the 

 fourth and fifth fingers have each three phalanges, the second and 

 third have each two. Their shape is not \xnlike that of the human 

 phalanges. 



V. THE BONES OF THE HINDER EXTREMITY. 



A. Bones of the Pelvic Girdle (Fig-. 41). 



The pelvis has a characteristic V- shape, the pubic and ischiatic 

 bones of the two sides together forming- a vertical plate {a p), 

 which divides anteriorly into the two iliac bones (//). The pubic 

 and ischiatic bones being united by their median surfaces, one can 

 only speak of the pelvic cavity as the space between the two 

 ilia. 



1. The ilia, ossa il il (Fig. 42 il). In these a broader part or 



' I. c, n, 464. 



