302 ANIMAL HEAT. 



nearly all parts of a living plant, such as the green stems, the leaves, 

 the buds, and even the roots and fruit, generate a certain amount of 

 heat; the maximum temperature thus detected being about 0.28 above 

 that of the surrounding atmosphere. Subsequent observations have 

 shown that in certain periods of vegetative activity, as in the processes 

 of germination and flowering, the development of heat is much more 

 rapid. In the malting of barley, when a considerable quantity of the 

 germinating grain is piled in a mass, its elevation of temperature may 

 be readily distinguished, both by the hand and the thermometer. The 

 most striking example of heat-production in flowers is presented by 

 those of the Aracese (Calla, Indian turnip, Sweet flag) at the time of 

 fecundation, 1 which in warm weather ma}^ show a temperature of 4, 

 5, or even 10 above that of the surrounding air. 



The generation of heat is accordingly a phenomenon common to all 

 living organisms, whether animal or vegetable. When the mass of the 

 organized body is large in proportion to its extent of surface, the heat 

 thus produced is readily distinguishable both by the touch and by the 

 thermometer. When rapidly dissipated by increased extent of surface, 

 and especially by the evaporation of moisture, it is less easily detected, 

 but it exists in each case. In birds and mammalians it is more active 

 than in reptiles and fish ; and even in different species of animals belong- 

 ing to the same class, it is usually found that the normal temperature 

 of the body, like the other physiological phenomena, differs slightly, 

 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 produced 

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

 temperature which it will produce in a certain volume of water. Prof. 

 John C. Draper 2 found that the human body, having a volume of about 

 85 litres (3 cubic feet) and a weight of 81.65 kilogrammes (180 pounds 

 avoirdupois), by remaining at rest in the bath for one hour, could raise 

 the temperature of 212 kilogrammes of water 1.1 1 ; 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 2.11. But as 

 the temperature of the body, in the observation quoted, was lowered 

 0.55 while in the bath, the heat actually generated would be capable 

 of warming the body itself, or an equal volume of water, 2.22. This 

 would be equivalent to 188.7 heat units, 3 produced by the human body 

 in the course of one hour, or 2.31 heat units for every kilogramme of 

 bodily weight. 



The experiments of Senator 4 on the heat-producing power in dogs 



1 Sachs, Traite de Botanique. Paris, 1874, p. 847. 



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



3 A heat unit is the quantity of heat required to raise the temperature of one 

 kilogramme of water from to 1 of the centigrade scale. 



4 Archiv fur Anatomic, Physiologic, und Wissenschaftliche Medicin. Leipzig, 

 1872. 



