CALORIMETERS. 



845 



the most exact of the modern methods are modifications of this. 1 D'Arsonval, 2 

 in 1886, introduced the differential air calorimeter, which has this great advan- 

 tage, that the loss of 

 heat by conduction 

 and radiation from 

 the calorimeter con- 

 taining the animal is 

 compensated by a 

 similar loss from a 

 dummy calorimeter of 

 similar size and con- 

 struction. This 

 method has been em- 

 ployed, and still fur- 

 ther modified, by 

 Rosenthal 3 and 

 Rubner, 4 but it will 

 suffice here to describe 

 only the latest form, 

 that introduced by 

 Haldane, Hale White, 

 and Washbourn. 5 In 

 this calorimeter (Fig. 

 85) the heat produced 

 by the animal in one 



chamber is balanced by FlGi 82. Diagram of Dulong's water calorimeter, 



the heat given off by a 



hydrogen flame burning in another similar chamber. The amount of hydrogen 



burnt is estimated, and, 

 knowing the heat of 

 combustion of hydro- 

 gen, one can calculate 

 the calories produced 

 by the quantity of 

 hydrogen used in the 

 experiment; this num- 

 ber of calories is equal 

 to those given off by 

 the animal. The cal- 

 orimeter is so arranged 

 that at the same time 

 it serves as a respira- 

 tory apparatus, and the 

 determination of 

 the intake of oxygen 

 and output of carbon dioxide checks the result of the calorimetric observa- 

 tion. 



1 Rosenthal, Arch. f. Physiol., Leipzig, 1878, S. 349 ; Richet, Arch, de physiol. norm, 

 et path., Paris, 1885, tome vi. p. 237 ; Mosso, Arch. f. exper. Path. u. Pharmakol., Leipzig, 

 1890, Bd. xxvi. S. 316. 



2 Journ. de I'anat. et physiol. etc., Paris, 1886, tome xxii. 



3 Arch.f. Physiol., Leipzig, 1888, S. 1. 



4 " Calorimetrische Methodik," Marburg, 1891; Beitr. z. Physiol. Carl Ludwig 

 z. s. 70 Geburtst., Leipzig, 1887 ; Ztschr. f. Biol., Miinchen, 1893-94, Bd. xxx. 

 92. 



5 Journ. Physiol., Cambridge and London, 1894, vol. xvi. p. 123; Hale White, 

 Croonian Lectures, Lancet, London, 1897, vol. ii. ; and Brit. Med. Journ., London, 1897, 

 vol. ii. p. 11. 



FIG. S3. 



F. Layer of felt. 

 C. Cage. 



jram of air calorimeter (Haldane, Hale 

 A r hite, and Washbourn). 



A. Tubes for ventilation. 

 H. Hydrogen flame. 

 M. Manometer. 



