THE FROG 6 1 



the two, the centrale. In the distal row we find, be- 

 ginning on the radial or thumb side, two small bones 

 corresponding respectively to the rudimentary thumb and 

 the first finger; these we call distals i and 2. There is a 

 much larger crescentic bone which represents distals 3, 4 

 and 5 fused together. 



The hand or manus exclusive of the wrist has four com- 

 plete digits, and a rudimentary thumb. Adjoining the car- 

 pal bones are five metacarpals ; the small first metacarpal 

 on the preaxial side represents the thumb (pollex). The 

 second and third metacarpals are followed by two phalanges 

 each, the fourth and fifth by three each. The phalanges 

 form the fingers. 



Draw (X 2) the manus, including the wrist. 



3. The pelvic girdle or pelvis as a whole is V-shaped. 

 In the adult frog the girdle is placed very obliquely, so as to 

 be nearly parallel to the vertebral column instead of at right 

 angles to it. The two limbs of the V diverge anteriorly and 

 are fastened to the strong backwardly-directed transverse 

 processes of the ninth or sacral vertebra. Each lateral half 

 of the pelvic girdle is composed of three parts, which meet 

 in the acetabulum, a rounded cavity which receives the 

 head of the femur and forms with it the hip-joint. The 

 three parts are: 



The ilium, the long bone forming a limb of the V. Ob- 

 serve on its dorsal surface a prominent ridge, the iliac crest. 

 The ilium is attached in front to the tip of the transverse 

 process of the ninth vertebrae; posteriorly it forms the an- 

 terior and dorsal half of the acetabulum. Posteriorly the 

 two ilia meet and are united in the median plane to form the 

 iliac symphysis. 



