35 



support the due arterialization of the blood ; and hetice animals con- 

 fined in such air are in a statė peculiariy liable to be aft'ected by any 

 great or unusual dcpression oi temperature. It is probably on ac- 

 count of their breathing air much contaminated by carbonic acid gas 

 that persons sleeping near limekilns are so frequently frost-bitten. 

 In repositories for animals vvhich are much freąuented the air is vi- 

 tiated by ihe respiration of the visitors also, who, moreover, impart a 

 heat to the rooms \vhich is indicated by the thermometer, but is not 

 beneficial but noxious to the animals. The air should be continually 

 renevved, and wheii its temperature is to be raised it should be heated, 

 wherepracticable,by a furnace placed in alūwer apartment previonsly 

 to being admitted into the repository, from vvhich ample exit should 

 be allowed at the top : in this manner an effective ventilation on just 

 and scientifir principlcs would be established. 



Exhaustion from fatigue is one of the causes vvhich render persons 

 ascending heights more susct-ptible to the impression of cold ; ex- 

 haustion from hunger produces the šame efl'ect : Mr. Hunter has 

 shown that an animal vvhich had fasted for some time vvas more 

 affected by cold than one that vvas vvell fed, the reduction of tempe- 

 rature in the latter being 16° and 18°, in the former 18° and 21°. 

 The means of counteracting these efFects in menageries are obvious ; 

 but it is particularly necessary to attend to them in the importation of 

 tropical animals, so many of vvhich perish in beating up Channel, the 

 effect of the lovv temperature being increased by the exhaustion from 

 the fatigue of the voyage. Hence in the Channel not only should 

 cold be particularly guarded against, but additional food should be 

 supplied. 



Young animals are generally very susceptible of the efFects of cold, 

 as has been shown by the experiments of M. Ed\vards. Thus, young 

 birds vemoved from the nešt become quickly of the šame temperature 

 as the surrounding atmosphere, The young of those Mammalia vvhich 

 are born blind are eąually obnoxious to cold, their blood being im- 

 perfectly arterialized, ovving to iheforamen ovale remaining open for 

 some time ; the young of the other Mammalia retain the temperature 

 of the adult animal. This makes it very important that if any of the 

 feline or similar races of animals breed in European menageries, their 

 dens should be peculiariy vvarm : the probability of preserving them 

 will also of course be considerably increased if the young are produced 

 in summer, or even in spring. 



Season, as has been shown by the experiments of M.Edveards, ex- 

 ercises a considerableinfluenceon the susceptibilityof animals for cold; 

 a much greater degree being borne with impunity in vvinter than in 

 summer. This is apparently analogous to what occurs in the vegetable 

 kingdom : atree vvhich vvill bearin winter a temperature of — 20° with- 

 out injury vvill be scathed as if by lightning, and perhaps die, if in sum- 

 mer it be exposed to 32° or 30°. Many animals, in captivity especially 

 (the Syltiadce as a familiar instance,) are as susceptible of cold as these 

 trees ; a draft of cold air or a frosty night vvill frequently produce on 

 them eft'ects from vvhich tliey never recover. As this susceptibiiitv itt 

 so considerably increased during summer, especiai care should be 



