538 EVOLUTION OF HEAT, LIGHT, AND ELECTRICITY. 



429. Exposure to a very elevated temperature, 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 statement? already made, in regard to 

 the variation in the heat of the body with changes in atmospheric tempera- 

 ture (425). In the experiments of MM. Berger and Delaroche, 1 it was 

 found that, after the body had been exposed to air of 120 during 17 min- 

 utes, a thermometer placed in the mouth rose nearly 7 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 vapor 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 circum- 

 stances, to a degree very much greater than this. In one of the experi- 

 ments of Drs. Fordyce and Blagden, 2 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 inclosing them in air 

 heated from 122 to 201, until they 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 a sudden elevation to this degree must be fatal. 3 

 This elevation would be obtained comparatively soon in a moist atmosphere; 

 partly because of the greater conducting power of the medium, but princi- 

 pally on account of the check which is put upon the vaporization of the 

 fluid secreted by the skin. Even here, however, custom and acquired con- 

 stitution have a very striking influence; for whilst the inhabitants of this 

 country are unable to sustain, during more than 10 or 12 minutes, immer- 

 sion in a vapor-bath of the temperature of 110 or 120, the Finnish peas- 

 antry remain for half an hour or more in a vapor-bath, whose temperature 

 finally rises even to 158 or 167. Pouchet 4 has endeavored to show that, 

 when small animals are exposed to cold, death results from changes occur- 

 ring in the blood-corpuscles; Walther 5 has referred the fatal issue to anaemia 

 of the nervous system. But Bernard, 6 who has made many experiments on 

 this point, attributes it to the toxic influence of heat on the striated muscular 

 tissue, which speedily occasions the arrest of the cardiac and respiratory 

 movements. Death occurs in cold-blooded animals on sudden exposure to 

 a temperature of from 98 to 102 F., in Mammals on exposure to a tem- 

 perature of 109-111 F., and in Birds of 120-122 F. On examination 

 the heart is found to have stopped, though it long continues to beat in ordi- 

 nary asphyxia, and neither it nor any of the striated muscles respond to 

 electrical or other stimuli, whilst cadaveric rigidity, due apparently to co- 

 agulation of the myelin, sets in with wonderful rapidity. The unstriated 

 muscular fibres seem to be powerfully stimulated by these degrees of heat. 



1 Experiences sur les Eft'ets qu'une forte Chaleur produit sur 1'Economie; Paris, 

 1805; and Journal de Physique, tomes Ixiii, Ixxi, et Ixxvii. 

 ' Philosophical Transactions, 1775. 



3 Bernard (Com pies Rendus de la Soeiete de Biologic, 1859, p. 51) attributes the 

 death of the animals in these and similar experiments to a condition analogous to 

 rigor mortis <>f the ht-art being established. He found the auricles filled with blood, 

 but the ventricles lirmly contracted and empty. 



4 Journal de 1' Anatomic, Jan. 1800. 6 Centralblatt, April, 18G6. 

 6 Lecons, in the Revue Scientittque, 1871, p. 183 et seq. 



