HYBERNATION. 



403 



Jtahnmb birds recorded by M r Xeill, in his T< wr through Orkney 

 which </ Shetland, as having been observed in the case of 



*"*? the land-rail, or corncrake as it is railed in Scotland. 

 ^ j^, " I made," says he, " frequent inquiry, whether corn- 

 crakes had been seen to migrate mm Orkney, but 

 could not learn that such a circumstance had been ob- 

 served. It is the opinion of the inhabitants, indeed, 

 that they are not able to undertake a flight across the sea. 

 Mr Yorston, the farmer at Aikerness, further related a 

 curious fact, rather leading to the conclusion that they do 

 not migrate. In the course of demolishing a hill-dyke, 

 (i. e. a mud wall,) at Aikerness, about midwinter, a 

 corncraHf was found in the midst of the wall. It was 

 apparently lifeless ; but, being fresh to the feel and 

 smell, Mr Yorston thought of placing it in a warm si- 

 tuation, to see if it would revive. In a short time it 

 began to move, and in a few hours it was able to walk 

 about. It lived for two days in the kitchen, but would 

 not eat any kind of food. It then died, and became 

 putrid. I do not assert that this solitary instance ought 

 to be regarded in any other light than as an exception 

 to the general rule of migration, till further observation 

 have determined the po: 



These are the only instance* with which we are ac- 

 qwfated of actual torpidity having occurred among 

 the feathered tribe*. They seem calculated to remove 

 all doubt a* to the fact, while they point out to u* the 

 i of nature in extreme case* to pre- 

 Thu* when bird* from disease or 

 youth, are incapable of performing the 

 ordinary migration* of their tribes, they become dor- 

 mant during the winter months, until the beat of spring 

 restore* to them a supply of food and an agreeable 

 temperature. 



Hitherto we have been considering the torpidity 

 which warm-blooded animal* experience. Several cold 



made of hyberna- 



The period of the year at which RrpTiLK* prepare 

 for this slate of lethargy varies in the different *peesM. 

 In general, when the temperature of the air sinkt below 

 the 50th degree of Fahrenheit. the*e animal* begin their 

 winter slumber*. They adopt sianilar precautions as the 

 mammalia, in selecting proper pUcc* of retreat, to pro- 

 tect that* from their enemies, and pmerve them 



dden alt 



* of tampsrature. 

 into the soft mud. 



Thow which inha- 

 while those which 



bit the water* sink 



live eo the land enter the bole* and ere rice* of rocks, 



or other place* where the heat is bat little affected by 



rhangfi in the temperature of the 



provided, they obey the impulse, 



atmosphere. Thus 



Aa the temperature of these anhnaU depend* on the 

 I medin, they do not exhibit any prculia- 

 respect to it. When the air i* under SO, 



torpid, and suffer their ' 

 ture to sink as low a* the freezing point. When re- 

 duced below this, either by natural or artificial mean*, 

 the vital principle i* in danger of being extinguished. 

 In this torpid state, they respire very slowly, as the cir- 

 culation of the blood can be carried on independent of 

 the action ef the lungs. Even in a tortoise kej 

 during the winter by s genial temperature, the f 

 eff aspiration wa* observed to be dhnimiahsd. 



The circulation of the blood i* diminiahed, in proper. 

 tion to the degree of cold to which these torpid reptile* 

 are exposed. Spallansani counted from eleven to twelve 

 pulsation* in a minute in the heart of a make at the 

 temperature of *&', whose pulte in general in warm 



Animal:. 



which 



btcomc 



Torpid. 



weather gives about thirty beats in the same period. 

 Dr Reeves made some very interesting experiments on 

 the circulation of the toad and frog. " 1 observed,'' he 

 says, " that the number of pulsations in toads and frogs 

 was thirty in a minute, whilst they were left to them- 

 selves in the atmosphere of which the temperature was 

 53; when placed in a medium cooled to 40, the num- 

 ber of pulsations was reduced to twelve, within the 

 same period of time; and when exposed to a freezing 

 mixture at 26 3 , the action of the heart ceased alto- 

 gether." 



The powers of digestion are equally feeble during 

 torpidity as those of respiration or circulation. Mr John 

 Hunter conveyed pieces of worms and meat down the 

 throats of lizards when they were going to their winter 

 quarters, and, keeping them afterwards in a cool place, 

 on opening them at different periods, he always found 

 the substances, he had introduced, entire, and without 

 any alteration ; sometimes they were in the stomach, 

 at other times they hid passed into the intestines, and 

 some of the lizards that were allowed to live, voided 

 them toward the spring entire, and with very little al- 

 teration in their structure. 



The immediate cause of torpidity in reptiles has been 

 ascertained with more precision, than in the animals 

 belonging to the higher classes with warm blood. 

 This condition with them, does not depend on tin- 

 of the heart, the lungs, or the brain; for these dit!'.-r. nt 

 organs have been removed by Spallanzani, and still the 

 ammals became torpid, and recovered according to cir- 

 cumstances. Even after the l.lood had been withdrawn 

 from frogs and salamander*, the* exhibited the same 

 ymptom* of torpidity a* if the body had been entire, 

 and all tbe organ* capable of action. 



w ith thee animal*, U evidently the chief cau.-e 

 of their torpidity, acting on a frame extremely *en*ible 

 to it* impression*. During the continuance of a high 

 temperature, these animals remain active and li. 

 but when the temperature i* reduced towards 40 , they 

 become torpid, and in this condition, if placed in a si- 

 tuation when the temperature continues low, will re- 

 main torpid for an unknown period of time. Spallan- 

 xani kept Grog*, salamanders, and make*, in a torpid 

 Mate in an ice-house, where they remained three years 

 and a half, and readily revived when again exposed to the 

 influence of a warm atmosphere. These experiments give 

 countenance to those report* in daily circulation of toad* 

 being found enclosed in rtone*. These animal may have 

 entered a deep crevice of the rock, and during their 

 torpidity, been covered with sand, which has after- 

 wards concreted around them. Thus removed from 

 tbe maWnre of the heat of spring or summer, and in a 

 place where tbe temperature continued below the point 

 at which they revive, it is impossible to fix limits to the 

 period during which they may remain in this dormant 

 Mate. 



Since reptiles arc easily acted upon by a cold at- 

 mosphere, we find but few of those animals distribu- 

 ted in the cold countries of the globe; while in those 

 countries whose temperature U always high, these ani- 

 mal* are found of vast size, and of many different 

 kinds, and in great number*. 



The torpidity of the Molliuca has not been studied Molliuu. 

 with care. Those which are naked and reside on the 

 land, retire to boles in the earth, under the root* of 

 tree*, or among roots, and there screen themselves 

 from sudden change* of temperature. The different 

 kinds of land Testacea, such a* those belonging to the 

 genera Helix, Uulimu*, and Pupa, not only retire to 



