I.] THE FROG. 3 



ment constituting the web. The innermost and shortest 

 answers to the hallux, or great toe, in Man. 



At the base of the hallux, the integument of the sole 

 presents a small horny prominence, which overlies a bony 

 calcar ; sometimes there is a similar but smaller elevation 

 on the outer side of the foot: but there are no nails upon 

 the ends of any of the digits of either the pes or the manus. 

 Thickenings, or callosities, of the integument, however, occur 

 beneath the joints of the digits, both in the pes and the 

 manus. 



During the breeding season, the integument on the 

 palmar surface of the innermost digit of the manus, in the 

 male, becomes converted into a rough and swollen cushion. 

 This, in the Grass Frog, acquires a dark-brown or black 

 colour. 



The Frog, when at rest, habitually assumes a sitting pos- 

 ture much like that of a dog or cat. Under these circum- 

 stances the back appears humped, the posterior half being 

 inclined at a sharp angle with the anterior half. The ver- 

 tebral column, however, will be found to be straight, and the 

 apparent hump-back arises, not from any bend in the verte- 

 bral column, but from the manner in which the bones 

 of the hip-girdle are set on to the same. 



The walk of the Frog is slow and awkward, but it leaps 

 with great force, by the sudden extension of the hind-limbs, 

 and it is an admirable swimmer. 



In a living Frog, the nostrils will be seen to be alter- 

 nately opened and shut, while the integument covering the 

 under side of the throat is swollen out and flattened. The 

 sucking in and circulation of the air needed for the Frog's 

 respiration is connected with these movements. 



The upper eyelid of the Frog is large and covered with 

 ordinary pigmented integument, and it has very little 



