LESSON 48.] NUTRITION IN FISHES AND REPTILES. 169 



limbs to their utmost capacity, and creeps towards the insect in the 

 most stealthy, noiseless manner possible ; as soon as he arrives within 

 a certain distance of his victim, the tongue is thrown out so rapidly 

 that it escapes detection ; but the fly has been struck, glued to the 

 tongue by the mucus on the surface, and returns with it into the 

 Frog's mouth. 



741. The senses of hearing, sight, and smell, are wonderfully acute 

 in these animals. No one would believe that a fly alighting on the 

 surface of a carpet, would be accompanied by any appreciable sound, 

 and (so far as our sensations are concerned) this is quite true ; not 

 so with a frog, however ; the fly may alight at a distant part of 

 the room, and the frog's back be turned from that direction, yet he 

 hears it instantly, turns round, and proceeds to effect its capture, in 

 which he very rarely fails ! 



742. The mode by which a frog is enabled to seize its prey, is 

 in this wise : stimulated by the sight of it, the tongue becomes in- 

 jected with blood, through the influence of the imagination, until it 

 is quite turgid or erect ; at this instant, it can be thrown out and 

 used. The action is like letting the back of the hand fall quickly 

 from the elbow-joint, FIG 



without moving the 

 wrist, and allowing it 

 quickly to rebound. 



743. The process 

 requires to be swift, 

 for the breathing of 

 the frog is suspend- 

 ed so long as the 

 mouth remains open. 



744. There is not 

 in nature a more 

 harmless or valuable 



animal than a frog, nor one, whose presence in gardens should be 

 so much encouraged, for they consume only insects, spiders, and 

 slugs, and the quantity of these they destroy is quite incredible. 



745. It has been remarked that the teeth have a prehensile 

 character in the frogs, but this cannot be demonstrated in Fig. 269, 

 copied from a minutely injected preparation of the palate of a frog, 

 because the spectator looks directly down upon the teeth, whereby 

 the pointed apices escape detection ; moreover, he desires to see the 

 blood-vessels, to do which, cuts off (apparently) the points of the 



