ANIMAL HEAT. 



659 



To render the comparison of the mean sums 

 obtained more certain, we shall confine our- 

 selves to the observations of the inquirer just 

 quoted, made upon the same individuals at 

 different temperatures. The following series is 

 after the data supplied by Dr. Davy : 



Temperature of the air. Mean temperature of Jive 



men. 

 15, 5 (60 F ) ..... . 36, 85 (98 F.) 



25, 5 (78 F.) ....... 37, 16 (99 F.) 



26, 4 (79 F.) ....... 37, 32 (99 5, F.) 



26, 7 (80 F.) ....... 37, 58 (100 F.) 



27, 8 (82 F.) ....... 37, 70 (100 5, F.) 



It is apparent that these differences, even the 

 extremes, do not surpass the limits of the 

 variations which the same individual exhibits, 

 or may experience spontaneously under the 

 same temperature of the air. But when it is con- 

 sidered that these differences are mean results, 

 forming a series increasing with the rise of the 

 external temperature, it is impossible to doubt 

 of their standing in the relation to one another 

 of cause and effect. If this dependence and 

 connection actually exists, we must allow that 

 it is very little obvious at the temperatures 

 within the limits of which these observations 

 were made ; for whilst the temperature of the 

 air varied to the extent of 12, 3 c., the changes 

 in the mean temperature of the body did not 

 exceed 0, 9. Such slight differences being apt 

 to leave uncertainty in the mind as to the cause 

 producing them, we shall confirm the impres- 

 sion they are nevertheless calculated to make 

 by citing others, for which we are indebted to 

 Dr. Reynaud, surgeon of the corvette La 

 Chevrette, in a voyage of discovery in the 

 Asiatic seas undertaken in the year 1827. The 

 instruments used were furnished by the best 

 makers of Paris, and were compared by M. 

 Arago with those of the Observatory ; and the 

 observations were made conjointly with M. 

 Blosville, lieutenant of the vessel, charged by 

 the Academy of Sciences of Paris with various 

 researches in natural philosophy. 

 Mean temperature of the*^ 

 body deduced from ob- j 

 servations four times re- 

 peated upon each of eight 



_ 

 men, under the torrid 37 



. . , 

 37 > H 



T? \ 



zone, the external tempe- 



rature varying from 26 



to 30 c. (79, 86 F.)J 

 Mean temperature of the"^ 



same eight men observed 



three times in the tern- 



perate zone, the external 



temperature varying from 



12 to 17 (53to62F.)J 



These results confirm those of Dr. Davy by 

 so much the more as they were made within 

 the same limits of external temperature. The 

 mean rise of the temperature of the body un- 

 der the influence of that of the air is also 

 equally confirmed ; but the amount is still less 

 than as given by the English observer. 



It seems impossible, then, to doubt that the 

 natural variations in the temperature of the air 

 affect that of the body of man ; but this is 

 only in a very trifling degree, at least within the 



limits of temperature in which any extant ob- 

 servations have been made. It is greatly to be 

 regretted that neither of the observers quoted 

 had opportunities of ascertaining the effects of 

 much lower temperatures than those they have 

 given. There are, it is true, many isolated ob- 

 servations made by voyagers in the Arctic 

 regions, both upon animals and man, and 

 although conducted in no regular series, or as 

 points of comparison with one another, 

 they still lead to the same general result, 

 namely, that great differences in the tempera- 

 ture of the air cause slight differences in the 

 temperature of the body of animals. Thus, in 

 the voyage of Captain Parry it was observed 

 that the temperature of the Mammalia was very 

 high. With the external thermometer at 

 29, 4 ( 21, F.), the temperature of the 

 white hare was + 38, 3 (101 F.). With the 

 thermometer at 32, 8 (27 F.), the tempe- 

 rature of a wolf was + 40, 5 (105 F.); the 

 temperature of the Arctic fox, under nearly the 

 same circumstances, namely, when the thermo- 

 meter was standing at 35 ( 31 F.), was 

 as high as -f- 41 5 (107 F.). Similar obser- 

 vations have since been made in the same high 

 latitudes upon man. 



The variations in the temperature of warm- 

 blooded animals according to that of the seasons 

 has been studied by the present writer, who con- 

 firms the results just stated. The experiments 

 of the writer were made upon a great num- 

 ber of sparrows recently taken at different 

 seasons of the year, which is preferable to 

 keeping these creatures in captivity for any 

 length of time. The mean temperature of 

 these birds rose progressively from the depth 

 of winter to the height of summer, within the 

 limits of from two to three degrees centigrade. 

 The observations made on sparrows exhibited 

 the greatest differences. In the month of Feb- 

 ruary the mean temperature of these birds was 

 found to be 40, 8 (105 F.) ; in April 42 

 (108 F.), in July 43, 77 (111 F.). The 

 temperature from this time began to decline, 

 and followed, in the same ratio in which it had 

 increased, the sinking temperature of the year. 



Influence of media upon temperature. The 

 media in which animals live do not act solely 

 in the ratio of their temperature, but also by 

 virtue of the intensity of their cooling or heating 

 power. Thus air and water at the same 

 degree of heat will have a very different influ- 

 ence on the temperature of the bodies plunged 

 in them. The power of air in heating or 

 cooling is commonly known to be very inferior 

 to that of water. Bodies acquire or lose tem- 

 perature much more slowly in air than In water. 

 A water-bath according to its temperature com- 

 municates sensations of heat or cold far more 

 rapidly and powerfully than an air-bath. 

 The writer and M. Gentil made the following 

 experiment: A young man seventeen years of 

 age, of strong constitution and in good health, 

 after remaining for twenty minutes in a bath 

 the water of which marked 13 R. (61, 5 F.), 

 whilst the air was 14, R. (63 F.), half an 

 hour afterwards was found to have lost half a 

 degree of his original heat in the mouth and 



2x2 



