70 



ANIMAL CHEMISTRY. 



animal body cannot change, if the amount 

 of inspired oxygen increases in the same 

 ratio as the loss of heat by external cooling. 



Two individuals, carnivora, of equal 

 weight, exposed to unequal degrees of cold, 

 lose, in a given time, by external cooling, 

 unequal quantities of heat. Experience 

 teaches, that if their peculiar temperature 

 and their original weight are to remain un- 

 altered, they require unequal quantities of 

 food j more in the lower temperature than 

 in the higher. 



The circumstance that the original weight 

 remains the same, with unequal quantities 

 of food, obviously presupposes, that in the 

 same time a quantity of oxygen proportioned 

 to the temperature has been absorbed ; more 

 in the lower than in the higher temperature. 



We find that the weight of both indivi- 

 duals, at the end of 24 hours, is equal to the 

 original weight. But we have assumed 

 that their food is converted into blood ; that 

 the blood has served for nutrition ; and it is 

 plain, that when the original weight has 

 been restored, a quantity of the constituents 

 of the body, equal in weight to those of the 

 food, has lost its condition of life, and has 

 been expelled in combination with oxygen. 



The one individual, which, being exposed 

 to the lower temperature, consumed more 

 food, has also absorbed more oxygen; a 

 greater quantity of the constituents of its 

 body has been separated in combination 

 with oxygen; and, in consequence of this 

 combination with oxygen, a greater amount 

 of heat has been liberated, by which means 

 the 'neat abstracted has been restored, and 

 tne proper temperature of the body kept up. 



Consequently, by the abstraction of heat, 

 provided there be a full supply of food and 

 free access of oxygen, the change of matter 

 must be accelerated; and, along with the 

 augmented transformation, in a given time, 

 of living tissues, a greater amount of vital 

 force must be rendered available for mecha- 

 nical purposes. 



With the external cooling, the respiratory 

 motions become stronger; in a lower tem- 

 perature more oxygen is conveyed to the 

 blood ; the waste of matter increases, and if 

 the supply be not kept in equilibrium with 

 this waste, by means of food, the tempera- 

 ture of the body gradually sinks. 



But, in a given time, an unlimited supply 

 of oxygen cannot be introduced into the 

 body ; only a certain amount of living tissue 

 can lose the state of life, and only a limited 

 amount of vital force can be manifested in 

 mechanical phenomena. It is only, there- 

 fore, when the cooling, the generation of 

 force, and the absorption of oxygen are in 

 equilibrium together, that the temperature 

 of the body can remain unchanged. If the 

 loss of heat by cooling go beyond a certain 

 point, the vital phenomena diminish in the 

 same ratio; for the temperature falls, and 

 the temperature must be considered as a 

 uniform condition of their manifestation. 



Now experience teaches, that when the 



temperature of the body sinks, the power of 

 the limbs to produce mechanical effects (or 

 the force necessary to the voluntary motions) 

 is also diminished. The condition of sleep 

 ensues, and at last even the involuntary 

 motions (those of the heart and intestines, 

 for example) cease, and apparent death -or 

 syncope supervenes. 



It is obvious that the-cause of the genera- 

 ,tion of force, namely, the change of matter, 

 is diminished, because, with the abstraction 

 of heat, as in the plant by abstraction of 

 light, the intensity of the vital force di- 

 minishes. It is also obvious that the mo- 

 mentum of force in a living part depends 

 on its proper temperature; exactly as the 

 effect of a falling body stands in a fixed 

 relation to certain other conditions ; for ex- 

 ample, to the velocity attained in falling. 



When the -temperature sinks, jthe vital 

 energy diminishes ; when it again rises, the 

 momentum of force in the living parts 

 appears once more in all its original in 

 tensity. 



The production of force for mechanical 

 purposes, and the temperature of the body, 

 must, consequently, bear a fixed relation to 

 the amount of oxygen which can be absorbed 

 in a given time by the animal body. 



The quantities of oxygen which a whale 

 and a carriers horse can inspire in a given 

 time are very unequal. The temperature, 

 as well as the quantity of oxygen, is much 

 greater in the horse. 



The force exerted by a whale, when 

 struck with the harpoon, his body being 

 supported by the surrounding medium, and 

 the force exerted by a carrier's horse, which 

 carries its own weight and a 'heavy burden 

 for eight or ten hours, must both bear the 

 same ratio to the oxygen consumed. If we 

 take into consideration the time during which 

 the force is manifested, it is obvious that the 

 amount of force developed by the horse is 

 far greater than in the case of the whale. 



In climbing high mountains, where, in 

 consequence of the respiration of a highly 

 rarefied atmosphere, much less oxygen is 

 conveyed to the blood, in equal times, than 

 in valleys or at the level of the sea, the 

 change of matter diminishes in the same 

 ratio, and with it the amount of force avail- 

 able for mechanical purposes. For the most 

 part, drowsiness and want of force for me- 

 chanical exertions come on ; after twenty or 

 thirty steps, fatigue compels us to a fresh 

 accumulation offeree by means of rest (ab- 

 sorption of oxygen without waste of force 

 in voluntary motions.) 



By the absorption of oxygen into the sub- 

 stance of living tissues, these lose their con- 

 dition of life, and are separated as lifeless, 

 unorganized compounds; but the whole of 

 the inspired oxygen is not applied to these 

 transformations: the greater part serves to 

 convert into gas and vapour all matters 

 which no longer belong to the organism; 

 and, as formerly mentioned, the combina- 

 tion of the elements of such compounds 



