852 ANIMAL HEAT. 



result that it quickly boiled, owing to the absence of evaporation; 

 whereas the water in the other jar rose to 60, but did not boil, evapora- 

 tion taking place freely from the surface and thus cooling the water. 

 Upon the loss of heat by evaporation Crawford, 1 in 1781, made some 

 interesting experiments upon frogs ; he compared the rates of warming 

 of a dead and a living frog by exposure to warm air and to warm water, 

 and found that the temperature of the former rose more rapidly than 

 that of the latter. 



In another experiment he found that, when the air was 25, the skin of a 

 living frog was 20, the stomach 21'4; when the water was 16'l, the skin of 

 a living frog was 16*2, the stomach 19'2. It is to be noted that when the 

 frog was kept in water its nose was above^the surface, so that it might breathe ; 

 in this way heat might be lost by evaporation from the lungs. Crawford, 

 however, concluded from his experiments that the cooling was not solely due 

 to evaporation, and that animals had the power of " producing cold." 



In 1810, Delaroche 2 published some instructive experiments, similar to 

 those of Blagden, to show the effect of evaporation. He placed an alcarraza 3 

 full of water at 35, and a rabbit whose temperature was 39 '7, in a stove 

 heated to 45 ; the temperature of the rabbit gradually rose to 43 '8, while 

 that of the alcarraza fell to 31'4, and remained stationary. In the second 

 experiment he placed a frog and two pieces of moist sponge in a stove heated 

 to 36 *5, and found at the end of an hour that the frog's temperature was 

 stationary at 28 '2, and that of the pieces of sponge at 27 "9 and 27 '6. 

 Delaroche contests the results of Crawford's experiments on frogs, and main- 

 tains that these animals quickly take the temperature of the water in which 

 they are placed, and that in this respect there is no difference between a dead 

 and a living frog. 



According to the calculations of Vierordt and Ludwig, from 10 to 20 

 per cent, of the total daily loss of heat in an adult man is due to 

 evaporation from the skin and respiratory tract. Further details on the 

 discharge of water from the skin and lungs are given in another part of 

 this work. 4 The following values for the discharge of moisture from 

 various parts of the human skin were observed by Waller : 5 



Palm of hand . 24 mgrms. per 20 sq. cm. (per 10 minutes)^ 

 Sole of foot . 14 ,, 



Forehead . 12 



Cheek ' ' /tempera- 



ture, 20". 



Axilla . . 10 



Popliteal space 10 



Forearm . .. 5 



Leg . . 5 



External 



The influence of the size of the body upon the regulation of tem- 

 perature. The importance of the relation between the surface of the 

 body and its mass, in respect to the loss and production of heat, was first 

 pointed out by Bergmann. 6 The bigger an animal the greater the ratio of 



1 Crawford, Phil. Trans., London, 1781, vol. Ixxi. p. 485. 



2 Delaroche, Journ. dephys., Paris, 1810, tome Ixxi. pp. 294-296. 



3 A porous jar used for keeping water cool in hot climates. See also Edwards, "De 

 rinfluence des agens physiques sur la vie," p. 84. 



4 "Chemistry of Respiration," this Text-book, vol. i. p. 711. 



5 " Proc. Physiol. Soc.," Journ. Physiol., Cambridge and London, 1894, vol. xv. For 

 further observations see Hale White, Croonian Lectures, Lancet, London, 1897, June 19 

 and 26, and Brit. Med. Journ., London, 1897, vol. i. p. 1654 et seq. 



6 "Gottinger Studien," 1847, Abth. 1, S. 595. 



