CHEMICAL THEORY OF ANIMAL HEAT. 883 



actual cause of animal heat, may likewise produce local evolutions of 

 heat. The formation from starch, of sugar, lactic acid, and oxalic acid, 

 imply successive acts of hydration, and so perhaps also do the changes 

 of albumen into gelatin, glycocoll, creatin, creatinin, and urea. But 

 a certain quantity of oxygen actually disappears in the body, and two 

 of the chief ultimate products of excretion, carbonic acid and water, 

 are oxidated, not simply hydrated. Urea alone can be considered such 

 a product, being of course imperfectly oxidized. The supposition that 

 hydration will explain the formation of all the animal heat, overlooks 

 the far larger amount of heat evolved in the ultimate oxidation of the 

 carbon and hydrogen, which leave the body as carbonic acid and 

 water ; nor does it explain the higher temperature of those animals 

 which consume a large quantity of carbon and hydrogen in their food. 



With regard to the human body, the estimates of Despretz were 

 made on the supposition that a Man, according to his weight, expired 

 seven times as much carbonic acid as the dog experimented on by him. 

 The quantity thus arrived at is much less than that computed by all 

 subsequent experimenters, being only equivalent to 5J oz. of carbon in 

 the 24 hours. Other observers have estimated the daily excretion of car- 

 bon in the form of carbonic acid, as 8 or 9 oz. The size or weight of 

 these persons has not been recorded. Vierordt's estimate in a number 

 of individuals of different heights ranges from 5 to 8 oz. In men of a 

 mean height of 5 feet 9| inches, Dr. Edward Smith estimates the quan- 

 tity at upwards of 7 oz. The calculations hereafter given for a person 

 5 feet 6J inches, yield a quantity somewhat exceeding 6 oz. of carbon 

 per day. These results are obtained by direct experiments on the 

 absolute quantity of carbonic acid expired by animals or Man. Lie- 

 big's estimate is still higher ; thus, the quantity of carbon in the daily 

 food being determined on the one hand, and that contained in the urine 

 and intestinal excretions on the other, the difference, which was taken 

 to represent the amount given off by the lungs and the skin together, 

 amounted to 13.9 Hessian ounces, or to upwards 15 oz. av., of which 

 J oz. might be exhaled from the skin, and 14J oz. from the lungs. 

 This large quantity was found in vigorous soldiers actively exercised 

 in the open air, and supplied with abundant food. In other examples, 

 viz., in prisoners compelled to labor, the quantity was about 11 \ oz. 

 av. ; whilst in a prison where no forced labor was practised, it was 

 about 9J oz. av. Similarly estimated, the carbon expired daily by 

 sailors in the Danish Navy was found to be about 10 oz. av. (Schar- 

 ling.) These results taken generally, so far confirm the chemical the- 

 ory of animal heat, that they nearly explain the deficiency of Jth or Jth 

 left by the daily combustion of 5J oz. of carbon, calculated to be elim- 

 inated by Despretz ; the excess of oxygen absorbed which unites with 

 hydrogen, and to a small extent with sulphur and phosphorus, may 

 explain the rest. 



The chemical theory of the production of animal heat by oxidation 

 is in harmony with the fact, that increased respiration increases the 

 amount of chemical decomposition in the body, and simultaneously, the 

 amount of heat produced. Thus, all the conditions connected with 

 age, sex, period of the day and season, as well as those relating to food, 



