576 GENERAL REVIEW OF THE NUTRITIVE PROCESSES. 



makes a great difference in the degree of elevation of temperature, which may 

 be sustained without inconvenience. Many instances are on record, of a heat 

 of from 250 to 280 being endured in dry air for a considerable length of 

 time, even by persons unaccustomed to a particularly high temperature ; and 

 persons whose occupations are such as to require it, can sustain a much 

 higher degree of heat, though not perhaps for any long period. The workmen 

 of the late Sir F. Chantrey have been accustomed to enter a furnace in which 

 his moulds were dried, whilst the floor was red-hot, and a thermometer in the 

 air stood at 350 ; and Chabert, the " Fire-king," was in the habit of entering 

 an oven whose temperature was from 400 to 000. It is possible that these 

 feats might be easily matched by many workmen who are habitually exposed 

 to high temperatures ; such as those employed in Iron-foundries, Glass-houses, 

 and Gas-works. In all these instances, the dryness of the air facilitates the 

 rapidity of the vapourization of the fluid, of which the heat occasions the secre- 

 tion by the cutaneous glands ; and the large amount of caloric which becomes 

 latent in the process, is for the most part withdrawn from the body, the tem- 

 perature of which is thus kept down. Exposure to a very elevated tempera- 

 ture, however, if continued for a sufficient length of time, does produce a 

 certain elevation of that of the body ; as might be expected from the state- 

 ments already made in regard to the variation in the heat of the body which 

 changes in atmospheric temperature ( 720). In the experiments of MM. 

 Berger and Delaroche, it was found that, after the body had been exposed to air 

 of 120 during 17 minutes, a thermometer placed in the mouth rose nearly 6 

 degrees above the ordinary temperature ; it may be remarked, however, that as 

 the body was immersed in a close box, from which the head projected (in 

 order to avoid the direct influence of the heated air on the temperature of the 

 mouth), the air had probably become charged with the vapour exhaled from 

 the surface, and had therefore somewhat of the effects of a moist atmosphere. 

 At any rate, the temperature of the body does not appear to rise, under any 

 circumstances, to a degree very much greater than this. In one of the expe- 

 riments of Drs. Fordyce and Blagden, the temperature of a Dog, that had 

 been shut up for half an hour in a chamber of which the temperature was 

 between 220 and 236, was found to have risen from 101 to about 108. 

 MM. Delaroche and Berger tried several experiments on different species of 

 animals, in order to ascertain the highest temperature to which the body could 

 be raised without the destruction of life, by enclosing them in air heated from. 

 122 to 201, until it died : the result was very uniform, the temperature of the 

 body at the end of the experiment only varying in the different species between 

 11 and 13 above their natural standard: whence it may be inferred, that an 

 elevation to this degree must be fatal. This elevation would be attained com- 

 paratively soon in a moist atmosphere ; partly because of the greater conducting 

 power of the medium ; but principally "on account of the check which is put 

 upon the vapourization of the fluid secreted by the skin. Even here, however, 

 custom and acquired constitution have a very striking influence ; for whilst 

 the inhabitants of this country are unable to sustain, during more than 10 or 

 12 minutes, immersion in a vapour-bath of the temperature of 110 or 120. 

 the Finnish peasantry remain for half an hour or more in a vapour-bath the 

 temperature of which finally rises to 158 or 167. Accurate experiments 

 are yet wanting, to determine the influence of humidity on the effects of cold 

 air. From experiments on young Birds incapable of maintaining their own 

 temperature, of which some were placed in cold dry air, and others in cold 

 air charged with moisture, it was found by Dr. Edwards that the loss of heat 

 was in both instances the same ; the effect of the evaporation from the surface 

 in the former case, being counterbalanced by the depressing influence of the 



