6 THE FROG CHAP. 



same length as- the third. All the toes are joined to- 

 gether by thin transparent webs, and, like the fingers, 

 have no nails. The name digit is conveniently applied 

 both to fingers and toes. Between the bases of the 

 thighs, at the hinder end of the trunk, is a small 

 aperture, the vent or anus. 



In the squatting posture the body is raised upon the 

 arms, which are kept slightly bent at the elbows, with 

 the fingers spread out and directed forwards. In this 

 position the innermost of the four fingers corresponds 

 with our own index-finger, the frog having no thumb. 

 The hind-limb, under similar circumstances, is bent into 

 a sort of Z, the knee being directed forwards and the 

 ankle-joint backwards. The toes are turned forwards, 

 and the inner one, which is the -smallest of all, corre- 

 sponds with our own great toe. 



Owing to the bent position of the limbs, we cannot 

 very well, as in our own arms and legs, speak of- their 

 upper and lower ends. It is therefore customary to call 

 the end of a limb, or of any division of a limb, which is 

 nearest to the trunk, the proximal end, that which is 

 furthest away the distal end. Thus the proximal end of 

 the fore-arm is the elbow region, the distal end of a 

 digit is its tip. 



The whole body, including head, trunk, and limbs, is 

 covered with a soft, slimy skin, of a brown colour, 

 irregularly spotted with brown or black on the upper or 

 dorsal surface, and whitish on the under or ventral surface. 

 The colouring is, however, not constant ; in a frog kept 

 in the dark the black spots increase to such an extent 

 that the whole animal becomes almost black, while if 

 kept in full daylight a corresponding brightening of 

 the tints takes place. Moreover, the spots and patches 

 of brighter colour are very variable : if you examine a 

 dozen specimens you will see at once that no two are 



