544 EVOLUTION OF HEAT, LIGHT, AND ELECTRICITY. 



pounds of water from the freezing to the boiling-point. Helmholtz estimated 

 the amount at 2700. 1 The mode in which the heat produced is applied, has 

 been estimated as follows : 



To the elevation to the temperature of the body of the food ingested, 2.6 per cent. 



To the warming of the air breathed, ....... 5.2 " 



To the vaporization of the water discharged by the lungs, . . . 14.7 " 



To the radiation from the body and evaporation from the skin, 77 5 " 



In this calculation Helmholtz estimated that one kilogramme of water 

 (==2.2 Ibs. avoird.) in evaporating from the skin and lungs took up or re- 

 quired 582 calories, its temperature being already nearly 100 F. Food 

 was considered to be upon the average about 20 F. cooler than the tem- 

 perature of the body, and to require the same amount of heat to warm it as 

 water. BarraP gives a somewhat different estimate, and considers that of 

 the total heat produced in a man at rest, which, in accordance with Helm- 

 holtz, he estimates at 2706.076 calories, 699.801, or 25.85 per cent., are lost 

 in the water evaporated from the skin and lungs; 100.811, or 3.72 per cent., 

 in warming the air breathed ; 52.492, or 1.94 per cent., in warming the food ; 

 33.020, or 1.22 per cent,, in the solid and fluid excreta; and 1819.952, or 

 67.22 per cent., by radiation and conduction and mechanical work. Beclard 3 

 estimates that a man daily develops sufficient heat to raise 55 Ibs. of water 

 from 32 to 212 F. 



436. The influence of the nervous system upon the temperature of the 

 body is well shown by the effects of section of the spinal cord. These effects, 

 however, are not constant, for such lesion is sometimes followed by an ele- 

 vation, and sometimes by a decline in the temperature. Thus, a case is re- 

 corded by Sir B. Brodie 4 in which the spinal cord having been so seriously 

 injured in the lower part of the cervical region that the whole of the nerves 

 passing off below were completely paralyzed, the heat of the body, as shown 

 by a thermometer placed in the groin, was not less than 111 F. ; and this, 

 notwithstanding that the respiratory function was very imperfectly performed, 

 the number of inspirations being considerably reduced, and the face livid. 

 Similar cases have been recorded by other observers. On the other hand, 

 when the spinal cord has been divided experimentally in animals, Sir B. 

 Brodie 5 and others have shown that the temperature of the body usually 

 falls with rapidity, even when artificial respiration is steadily maintained. 

 This difference, however, is probably due to the secondary conditions of the 

 experiment, for it is to be particularly noted that section of the spinal cord 

 below the medulla oblongata paralyses the vaso-motor centre, and conse- 

 quently produces hypememia of the capillaries of the body generally a con- 

 dition that would necessarily lead to increased production of heat. On the 



1 Or rather 2,700,000, but he considered a calory to be the quantity of heat required 

 to raise 1 gramme of water 1 C., instead of 1 kilogramme, which is 1000 grammes. 



2 Stat. China, des Animaux. Paris, 18-30. 



3 Physiol., 186-2, p. 561. 



4 Med. Gaz., June, 1836, and Physiolog. Researches, p. 121. 



5 Philosophical Trans., 1811. 1812, and Physiological Researches. Sec also the 

 confirmatory experiments of MM. Lc Gallois, Anuales de Chimie, 1817, and (Euvres, 

 t. ii, Chussat, Momoire sur 1'Innuence du Syst. Nerv. sur la Chaleur Animale ; and 

 TM'liesrhichin, lleiehert's Archiv, 1860, pp. 151-179. C. Bernard, Comptes Rendus, 

 185:5, t. xxxvi, pp. 414 and r.32. Sehiff, Untersuehungeri, Heft 3 ; Physiol. d. Nerven- 

 System, 1855. Brown-Sequard, Revue Suientif , 1871, p. '288. The remarkable case 

 recorded by llutehinson, Lancet, 1875, vol. i, p. 713; and that by Dr. Teale, already 

 referred to. Ileidenhain, Ueber Einwirkungen des Nervon-System atif die Ko'rpor- 

 temperatur, in Plluger's Archiv, Bd. iii, p. 504; and Weir Mitchell, Brown-Se"quard'3 

 Archives of Scient. and Tract. Med., 1873, No. 4. Schreiber, Piluger's Archiv, Bd. 

 viii, 187-, p. 670. 



