REPTILES GENERALLY. I J 



suspension of vital forces is something like what vegetation under- 

 goes. Circulation and respiration are arrested, and in mahy cases 

 it is difficult to decide whether life is extinct or not ; but with 

 the return of spring the sun causes the juices — whether animal or 

 vegetable — to flow once more, and the whole system is set in 

 working order again. Reptiles belong only to the tropical and 

 temperate climates. In the frigid zones they do not exist. The 

 suspension of animation during winter in the cooler latitudes is a 

 beneficent law of nature; for the food on which the smaller 

 reptiles usually subsist is also gone, and they conveniently hiber- 

 nate until insect life revives. Reptiles are long-lived; but as 

 they sleep so many months at a time, and exhaust themselves so 

 little, even during their liveliest seasons, there seems no reason 

 why life should not be prolonged. 



The circulation of reptiles is less complete than that of birds 

 and mammals, the blood being only partially aerated; mingled 

 arterial and venous blood is sent to the lungs and through the 

 system, no part of which is supplied with pure arterialised blood. 

 The heart in general is formed of at most three cavities instead of 

 four, two auricles and one ventricle ; the latter receiving the 

 blood from the two former, i.e., venous blood from the system 

 and aerated blood from the lungs, producing what we should call 

 poor blood, having fewer of the red corpuscles, and, in the animal, 

 a consequent sluggishness of movement, insensibility, and slow 

 organic functions. In intelligence reptiles rank only a little above 

 fishes. Their powers of endurance, however, are very great. 

 They can do without food for a long while, and even without 

 air, and do not appear to suffer from an injury which to the 

 higher animals would cause great pain ; as, for instance, the 

 lopping off of a finger, or even a hand, or an inch or so of 

 tail. Imagine the " to do " of a monkey under such cir- 

 cumstances. 



All reptiles are oviparous, producing young from an egg, the 

 covering of which may be membranous, leathery, or calcareous. 

 In some cases the young are born alive, but that is only because 

 the eggs have been already hatched within the parent. For the 

 different conditions the terms oviparous, viviparous, and ovovivi- 

 parous are used. All reptiles cast their skin at irregular periods, 

 at least once, but more frequently four or five times during the 

 year. This is called sloughing or desquamation ; the latter 

 word, as it signifies rather a coming off of the scales, is not always 

 applicable; for unless the creature is in adverse circumstances 

 the slough is cast entire. All the reptiles I have ever watched 

 under favourable conditions cast their coat entire, beginning at 



