834 



ANIMAL HEAT. 



estimation of the production of heat during a complex chemical change, 

 involving combination and decomposition, it is only necessary to 

 consider the first and final conditions of the substances, whatever may 

 have been the intermediate stages. 1 



The determination of the heat produced or absorbed by chemical 

 change is made by enclosing the acting substances in a chamber sur- 

 rounded by water or mercury, the rise or fall of temperature in which 

 indicates the amount of heat produced or absorbed, as the case may 

 be. 2 



The heat of combustion of substances of physiological interest has 

 been determined by various observers; 3 the following table gives the 

 values of some of the most important substances : 



The above table shows that the different foodstuffs have different 

 values as producers of heat, and from these it is possible to calculate 

 the physical value of one kind of food in terms of the others. The 



1 Hess, quoted from Rubner (Ztschr. f. BioL, Munchen, 1894, Bd. xxx. S. 135). 



2 For further details on such calorimeters, see Miller, "Chemical Physics," p. 338, and 

 Watts' "Dictionary of Chemistry," vol. iii. pp. 28, 103; Stohmann, Journ. /. prdkt. 

 Chem., Leipzig (2), Bd. xix. S. 115 ; Bd. xxxix. S. 503. 



3 Crawford, "On Animal Heat," 1788, 2nd edition, pp. 320, 333, 351 ; Favre and 

 Silbermann, Ann. de chim. et phys., Paris, 1842, tome xxxiv. p. 357 ; Frankland, London, 

 Edinburgh, and Dublin Phil. Mag., London, 1866, vol. xxxii. p. 182 ; Hermann, Ber. d. 

 deutsch. chem. Gesellsch., Berlin, 1868, S. 18, 84 ; Rubner, Ztschr. f. BioL, Munchen, 1885, 

 Bd. xxi. S. 357; Berthelot, Corny t. rend. Acad. d. sc., Paris, 1886, tome cii. pp. 1211, 

 1284. 



4 Calorie = the heat required to raise 1 grm. of water 1 C. ; kilo-calorie = 1000 calories^ 

 heat required to raise 1 kilo of water 1 C. 



5 Arch.f. d. ges. Physiol., Bonn, 1885, Bd. xxxvi. S. 230. 



6 Journ. f. prakt. Chem. , Leipzig, Bd. xliv. S. 336. 



7 Ztschr. f. BioL, Munchen, 1893-94, Bd. xxx. S. 88. 



8 Ibid., 1895, Bd. xxxi. S. 364. 



9 "Ueber die Verbrennungswarme organischer Substanzen," Leipzig, 1880. 

 10 Compt. rend. Acad. d. sc., Paris, 1889, tome cix. p. 759. 



