I.] THE FROG. 71 



e. The first digit (pollex) supported only by a small 

 metacarpal bone. 



d. The carpus. Proceed as directed at the outset, 

 and examine under a low power. Its elements 

 can be resolved into three sets. 



a. Proximal elements ; two in number, articulating, 

 side by side, upon the radius and ulna respec- 

 tively. 



/?. Distal elements; three in number. The outer 

 one gives articulation to the three outermost 

 digits ; and is mainly connected with the outer 

 element of the proximal series. The two inner 

 ones give articulation to the pollex and second 

 metacarpal respectively. 



y. The central element (centrale); pre-axial in posi- 

 tion, and wedged in between the two innermost 

 elements of the distal series and the correspond- 

 ing proximal piece. 



The hip girdle. 



a. Its general form : V-shaped, with the apex directed 

 backwards. It consists of paired elements which 

 unite in the middle line and are in direct articula- 

 tion with the vertebral column (sacrum). 



b. The fossa (acetabuluni) on each side, for articula- 

 tion of the hind-limb. 



c. Examine from the side. The whole will be seen 

 to be subdivided, by a triradiate fissure running 

 through the acetabulum, into three pieces, viz. 



a. The pubis; a small triangular wedge-shaped 

 piece (cartilaginous except in old frogs) ; ventral 



