380 SOURCES OF HEAT. 



fore an approximate estimate may be made as to the quantity of heat 

 produced by an organism from the amount of oxygen consumed in a 

 unit of time. An equal consumption of O corresponds with an equal 

 production of heat, whether it served for the oxidation of H or of C. 

 As a matter of fact, a relation exists between heat-production in the 

 animal body and the consumption of O, as between cause and effect. 

 Thus, cold-blooded animals, which consume little O, have a low bodily 

 temperature. Among warm-blooded animals i kilogram of living rabbit 

 takes up 0.914 gram of O within an hour and by this means maintains 

 its bodily temperature on the average at 38 C.; i kilogram of living 

 hen, on the other hand, consumes 1.186 grams of O in an hour and 

 maintains as a result an average temperature of 43.9 C. The amount of 

 heat produced is equally large whether the combustion takes place 

 slowly or rapidly. The activity of metabolism has, accordingly, an in- 

 fluence only upon the rapidity, but never upon the absolute amount, of 

 heat-formation. Also, the combustion of inorganic substances in the 

 body, such as that of sulphur into sulphuric acid, that of phosphorus 

 into phosphoric acid, constitutes a source of heat, although it be but 

 slight. According to Rubner this amounts to but 0.47 per cent, of the 

 heat. 



(b) In addition to the processes of combustion, however, all of those 

 chemical processes in the human body, as a result of which the total 

 amount of potential energy present is diminished, in consequence of 

 greater saturation of affinities of the atoms previously present, are 

 attended with the development of heat. Wherever the atoms combine 

 with saturated affinities for greater stability in their ultimate position 

 of rest, chemical potential energy is transformed into kinetic thermal 

 energy, as, for instance, in the alcoholic fermentation of grape-sugar 

 and other similar processes. 



Heat is produced also in the following chemical process : 



() The union of bases with acids. Here the character of the base determines 

 the amount of heat formed, while the character of the acid is without any influence. 

 Only when the acid, as, for instance, carbon dioxid, is not capable of neutraliz- 

 ing the alkaline reaction, is the production of heat smaller. Also, the forma- 

 tion of chlorin-combinations, as in the stomach, generates heat. 



(-3) The transformation of a neutral into a basic salt. In the blood the 

 sulphuric and phosphoric acids resulting from the combustion of sulphur and 

 phosphorus combine with the alkalies of the blood to form basic salts. The 

 decomposition of the carbonates of the blood by lactic and phosphoric acids 

 constitutes a double source of heat, namely through the formation of a new salt, 

 as well as through the release of carbon dioxid, which is in part absorbed by the 

 blood. 



(>-) The combination of hemoglobin with oxygen. According to Berthelot 

 the amount of heat produced in this way is equal to one-seventh of the total 

 amount formed in the body. 



In the chemical processes through which the body is provided with heat there 

 not rarely occur heat-absorbing intermediate transformations of the bodies. At 

 times, in order to bring about more complete saturation of the affinities, inter- 

 mediary atom-groups in themselves firmly united must first be broken up. In this 

 process thermal energy is consumed. Also in the breaking up of stable aggregate 

 states in processes of retrogressive metamorphosis heat is bound up. All of these 

 intermediary losses of heat, however, are extremely slight as compared with that 

 due to the development of the end-products. 



2. Physical processes may be mentioned as a second source of heat, 

 (a) The transformation of the kinetic mechanical energy of the viscera 

 furnishes heat, as the work done cannot be conveyed to the outside. 



