14 BATEAOHIANS. 



however, utter a sharp hissing noise, some species of Crocodiles 

 howl energetically, the Geckos are particularly noisy, and I'rogs 

 haye a well-known croak. In Reptiles and Batrachians the brain 

 is small, a peculiarity which explains their slight intelligence and 

 the almost entire impossibility of teaching them anything. They 

 can, it is true, be tamed ; but although they seem to know indi- 

 viduals, they do not seem to be susceptible of afi'ection : the slight 

 compass of their brain renders them very insensible, and this insen- 

 sibility to pain enables them to support mutilations which would 

 prove immediately fatal to most other animals. For instance, the 

 Common Lizard frequently breaks its tail in its abrupt movements. 

 Does this disturb him ? Not at all ! This curtailment of his being 

 does not seem to affect him ; he awaits patiently for the return of 

 the organ, which complaisant nature renews as often as it becomes 

 necessary. In thfe Crocodiles and Monitor Lizards, however, a muti- 

 lated part is not renewed, and the renovated tails of other Lizards 

 do not develop bone. In some instances, the eyes may be put 

 out with impunity, or part of the head may be cut off; these 

 organs will be replaced or made whole in a certain time with- 

 out the animal having ceased to perform any of the functions 

 which are still permitted to him in his mutilated state. A 

 Tortoise will continue to live and walk for six months after it 

 is deprived of its brain, and a Salamander has been seen in a very 

 satisfactory state although its head was, so to speak, isolated from 

 the trunk by a ligature tied tightly close round the neck. There is 

 another curious peculiarity in the history of Reptiles and Batra- 

 chians : each year as they awake from their state of torpor, they 

 slough their old covering, and thus each year renew their youth ; 

 so far as the skin is concerned, it is certain that they retain their 

 youth a very long time. Their growth is slow, and continues 

 almost through the whole duration of their existence ; they are, 

 moreover, endowed with remarkable longevity. This is not very 

 astonishing, if we consider that (at least in our latitudes) they 

 remain torpid for several months yearly ; thus using up less of the 

 materials of life than most animals, they ought, consequently, to 

 attaia a more advanced age. The activity of organization in Reptiles 

 and Batrachians is so slight that their stomachs feel less of the exi- 

 gencies of hunger; hence they rarely take nourishment ; they digest 



