MAMMALS. 607 



of lijlbernation varies in some degree according to climate in the 

 same species of mammals.) These animals before beginning their 

 winter's sleep are particularly fat ; when in the spring they again 

 emerge from their secret places they are much emaciated. The 

 respiration is interrupted by long intervals and is nearly suspended ; 

 the quantity of oxygen consumed during this state is very small. 

 Animal warmth is much diminished, and the temperature of the 

 internal parts falls to 7", 6°, or even 3° of the centigrade scale; 

 it appears to depend upon that of the surrounding air. The beats 

 of the heart are much less numerous ; the circulation, however, of 

 the blood, though much retarded, proceeds uninterruptedly in the 

 capillaries. During the complete hybernation the feeling is almost 

 entirely suspended; particular portions of the body retain their 

 irritability long after death. Hence it would seem that they are 

 not altogether in the wrong who maintain that the life of mam- 

 mals dm-ing hybernation sinks down into that of reptiles. On 

 the cause of this phenomenon various opinions have been offered, 

 of which some rest upon incorrect observations, others upon un- 

 demonstrated assumptions, and others again upon no foundation at 

 all. That, for example, the bile of these animals is less acrid, and 

 that on this account they can support hunger for a longer time, as 

 Saissy maintains, is an assumption without proof; that the thymus 

 gland during hybernation increases in bulk and compresses the 

 lungs, as PiiUNELLE believes, is a contested point, whilst (accord- 

 ing to Jacobson) it is not that gland but a mass remarkable for 

 the quantity of fat which penetrates it and oppresses the thorax ; 

 as little can the com-se of an artery through the stapes (Avhich Otto 

 discovered and held to be the cerebral carotid ') elucidate the phe- 

 nomenon, for the same distribution occurs also in species not subject 

 to winter-sleep. Whether the pulmonary cells be larger and the 

 capillaries of the lungs less fine, than in other mammals (Barkow), 

 seems to require confirmation. Thus do we abstain from further 

 record, comparison, or refutation of different opinions. The essence 

 of hybernation consists in temporary depression of the powers of 

 life from almost entire suspension of respiration. This is almost all 

 that can be said upon the subject. That the tanrec, the hedgehoo* 

 of Madagascar {Centetes Illig.), sleeps at the hottest time of the 



1 According to Hyrtl this artery is rather an arteria orhito-maxiUaris. 



