72 MAMMALIA. 



lateral membranes, although they always have clavicles. Their feet are 

 short, and their motions feeble ; the mammae are placed under the ab- 

 domen, and the penis in a sheath. None of them have a caecum, and in 

 walking they all place the w^hole sole of the foot on the ground. 



They differ from each other by the relative position and proportions of 

 their incisors and canines. 



Some have long incisors in front, followed by other incisors and canines, 

 all even shorter than the molares, a kind of dentition of which the Tar- 

 siers, among the Quadmmana, have already given us an example, and 

 which, to a small extent, approximates these animals to the Rodentia. 

 Others have large separated canines, between which are placed small in- 

 cisors, this being the most Usual disposition among the Quadrumana and 

 the Carnaria; and these two dentary arrangements are found in genera, 

 otherwise very much resembling each other in their teguments, the shape 

 of their limbs, and mode of life. 



Erinaceus, Lin. 



The body of the Hedgehog is covered with bristles instead of hairs. 

 The skin of their back is furnished with muscles, such as the animal, 

 when bending his head and paws towards the abdomen, can shut himself 

 up within, as in a bag, and present his bristles on all sides to the enemy. 

 The tail is very short, and there are five toes to each foot. There are six 

 incisors in each jaw, the middle ones being the longest, and on each side 



sented. In ordinary sleep, the Bat, Domiouse, or any other of the lethargic ani- 

 mals, experiences a certain well-marked loss of his respiratorj' powers; he breathes 

 less, and the temperature of his body diminishes quite perceptibly, so that he can 

 bear with impunity the abstraction of atmospheric air. Now, in the state of hyber- 

 nation, all these symptoms are aggravated — the respiration scarcely goes on at all; 

 and if an animal in this state is placed in a receptacle where the consumption of the 

 gas composing the air can be calculated, it is found that the amount which he ab- 

 sorbs is exceedingly small indeed. The learned gentleman, in these delicate expe- 

 riments, employs a mahogany box, with a glass lid, divided horizontally at its middle 

 part by a fold of strong ribbon. The dimensions of the receptacle should be such as 

 will merely contain the animal. The Bat or Dormouse, being in a state of hyber- 

 nation, should then be placed on the ribbon and inclosed by fixing the lid. A 

 thermometer, which has a cylindrical bulb, should next be passed tlirough an orifice 

 made on purpose in the box, on a level with the ribbon, and should lie beneath and 

 in contact with the upper part of the abdomen of the animal. It should then be left 

 in this situation, and not disturbed; but should be so fixed as that the gas indica- 

 tions should be seen without any interruption of the lethargy; and then those indica- 

 tions, compared with another thermometer hung up in the same apartment, will give 

 the variations of each. In pursuing his investigations, Dr. H. fomid that the power 

 of animals in a state of h3'bernation to sustain the want of atmospheric air, enabled 

 a dormant Bat to preserve life for eleven minutes when immersed in water, whereas 

 a Hedgehog, not donnant, died in three minutes when put into the water. A prac- 

 tical distinction of some importance is stated by Dr. Hall between the torpor of ani- 

 mals and their hybernation. The former is an accidental occurrence, arising from a 

 benumbed state of the sentient nerves, and a stiffened condition of the muscles, pro- 

 ceeding directly from cold, and capable of affecting all animals, whilst a defined set 

 of the manmaalia only is subject to hybernation, in which state the animal retains 

 its sensibility and power of motion unimpaired. — Eng. Ed. 



