260 FUNCTIONS OF NUTRITION. 



of heat is much more rapid. In the malting of barley, when a con, 

 siderable quantity of germinating grain is piled in a mass, its elevation 

 of temperature may be distinguished, both by the hand and the ther- 

 mometer. The most abundant heat-production by vegetables is in the 

 flowers of the Araceae (Calla, Indian turnip, Sweet flag) at the time 

 of fecundation,* which sometimes show a temperature of from 5 to 

 10 above that of the surrounding air. 



The generation of heat is, accordingly, a phenomenon common to all 

 living organisms. When the mass of the body is large in proportion 

 to its extent of surface, its heat is readily perceptible both by the 

 touch and by the thermometer. In, birds and mammalians the heat 

 production is more active than in reptiles and fish ; and even in differ- 

 ent species of the same class, it differs in degree according to the 

 special organization of the animal and the general activity of its 

 functions. 



Quantity of Heat in the Living Body. The quantity of heat pro- 

 duced in the body within a given time is measured by the increase of 

 temperature which it produces in a known volume of water. Draperf 

 found that the human body, with a volume of about 85 litres (3 cubic 

 feet) and a weight of 81.65 kilogrammes (180 pounds avoirdupois), by 

 remaining in the bath for one hour, could raise the temperature of 212 

 kilogrammes of water 1.11 ; which he estimates, assuming the specific 

 heat of the body to be about the same with that of water, would be 

 capable of warming the body itself 2.77. But as the temperature of 

 the body, in the observation quoted, was lowered 0.55 while in the 

 bath he heat actually generated would be capable of warming the 

 bod}*, or an equal volume of water, 2.22. This would be equivalent 

 to 188. T heat units, J produced by the human body in the course of one 

 hour, or 2.31 heat units for every kilogramme of bodily weight. 



In the experiments of Senator on the heat-producing power in dogs, 

 the animals were inclosed in a copper cage, through which ventilation 

 was kept up at a known rate, the temperature of the incoming and 

 outgoing air being noted at short intervals. The cage was surrounded 

 by a known volume of water, at from 26.5 to 29 C., and the whole 

 apparatus inclosed in an outer case made as non-conducting as possible ; 

 the heat actually lost from it being determined by preliminary obser- 

 vation. The internal temperature of the animal having been taken, 

 he was introduced into the cage and allowed to remain for a certain 

 time. The heat produced was ascertained by the increase of temper- 

 ature in the water surrounding the cage, the result being corrected 

 by that of the air used for ventilation, as well as by the variation in 



* Sachs, Trait6 de Botanique. Paris, 1874, p. 847. 



f American Journal of Science and Arts. New Haven, 1872, vol. ii. } p. 445. 



J A heat unit is the quantity of heat required to raise the temperature of one kilo- 

 gramme of water from to 1 of the Centigrade scale. 



$ Archiv fur Anatomic, Physiologic, und wissenschaftliche Medicin. Leipzig, 

 1872. 



