14 



ANIMAL CHEMISTRY. 



the phenomena of life. Wonders surround 

 us on every side. The formation of a 

 crystal, of an octahedron, is not less incom- 

 prehensible than the production of a leaf or 

 of a muscular fibre; and the production 

 of vermilion from mercury and sulphur is 

 as much aa enigma as the formation of an 

 eye from the substance of the blood. 



The first conditions of animal life are nu- 

 tritious matters and oxygen, introduced into 

 the system. 



At every moment of his life man is taking 

 oxygen into his system, by means of the 

 organs of respiration ; no pause is observ- 

 able while life continues. 



The observations of physiologists have 

 shown that the body of an adult man, sup- 

 plied with sufficient food, has neither in- 

 creased nor diminished in weight at the end 

 of twenty-four hours ; yet the quantity of 

 oxygen taken into the system during this 

 period is very considerable. 



According to the experiments of Lavoisier, 

 an adult man takes into his system, from the 

 atmosphere, in one year, 746 Ibs., according 

 to Menzies, 837 Ibs.' of oxygen; yet we find 

 his weight, at the beginning and end of the 

 year, either quite the same, or differing, 

 one way or the other, by at most a few 

 pounds. (1)* 



What, k may be asked, has become of 

 the enormous weight of oxygen thus intro- 

 duced, in the course of a year into the 

 hi man system? 



This question may be answered satisfac- 

 torily ; no part of this oxygen remains in the 

 system ; but it is given out again in the form 

 of a compound of carbon or of hydrogen. 



The carbon and hydrogen of certain parts 

 of the body have entered into combination 

 with the oxygen introduced through the 

 lungs and through the skin, and have been 

 give.n out in the forms of carbonic acid gas 

 and the vapour of water. 



At every moment, with every expiration, 

 certain quantities of its elements separate 

 from the animal organism, after having en- 

 tered into combination, within the body, 

 with the oxygen of the atmosphere. 



If we assume, with Lavoisier and Seguin, 

 in order to obtain a foundation for our cal- 

 culation, that an adult man receives into his 

 system daily 32oz. (46,037 cubic inches= 

 15,661 grains, French weight) of oxygen, 

 and that the weight of the whole mass of 

 his blood, of which 80 per cent, is water, is 

 24 Ibs. ; it then appears, from the known 

 composition of the blood, that, in order to 

 convert the whole of its carbon and hydro- 

 gen into carbonic acid and water, 64,103 

 grains of oxygen are required. This quan- 

 tity will be taken into the system of an adult 

 in four days five hours. (2) 



Whether this oxygen enters into combi- 

 nation with the elements of the blood, or 

 with other, parts of the body containing car- 

 bon and hydrogen, in either case the conclu- 



* The Numbers refer to the Appendix. 



sion is inevitable, that the body of a man 

 who daily takes into the system 32^ oz. of 

 oxygen, must receive daily in the shape of 

 nourishment, as much carbon and hydrogen 

 as would suffice to supply 24 Ibs. of blood 

 with these elements; it being presupposed 

 that the weight of the body remains un- 

 changed, and that it retains its normal con- 

 dition as to health. 



This supply is furnished in the food. 



From the accurate determination of the 

 quantity of carbon daily taken into the sys- 

 tem in the food, as well as of that propor- 

 tion of it which passes out of the body in 

 the faeces and urine, unburned, that is, in 

 some form in which it is not combined with 

 oxygen, it appears that an adult, taking 

 moderate exercise, consumes 13.9 oz. of 

 carbon daily. (3) 



These 13^% oz. of carbon escape through 

 the skin and lungs as carbonic acid gas. 



For conversion into carbonic acid gas, 

 oz. of carbon require 37 oz. of oxygen. 



According to the analyses of Boussingault 

 (Ann. de Ch. et de Ph. LXXI. p. 136) a 

 horse consumes in twenty-four hours 97 

 oz. of carbon, a milk cow 69^ oz. The 

 quantities of carbon here mentioned are 

 those given off from the bodies of these ani- 

 mals in the form of carbonic acid ; and it 

 appears from them that the horse consumes, 

 in converting carbon into carbonic acid, 13 

 Ibs. 3J oz. in twenty-four hours, and the 

 milk cow 11 Ibs. 10| oz. of oxygen in the 

 same time. (4) 



Since no part of the oxygen taken into 

 the system is again given off in any otner 

 form but that of a compound of carbon or 

 hydrogen; since, farther, the carbon and hy- 

 drogen given off are replaced by carbon and 

 hydrogen supplied in the food, it is clear 

 that the amount of nourishment required by 

 the animal body must be in a direct ratio to 

 the quantity of oxygen taken into the 

 system. 



Two animals, which in equal times take 

 up by means of the lungs and skin unequal 

 quantities of oxygen, consume quantities of 

 the same nourishment which are unequal in 

 the same ratio. 



The consumption of oxygen in equal 

 times may be expressed by the number of 

 respirations ; it is clear that, in the same in 

 dividual, the quantity of nourishment re- 

 quired mus-t vary with the force and num 

 ber of the respirations. 



A child, in whom the organs of respiration 

 are naturally very active, requires food uf- 

 tener than an adult, and bears hunger less 

 easily. A bird, deprived of food, dies on the 

 third day, while a serpent, with its sluggish 

 respiration, can live without food three 

 months and longer. 



The number of respirations is smaller m 

 a state of rest than during exercise or work. 

 The quantity of food necessary in both con- 

 ditions must vary in the same latio. 



An excess of food is incompatible with 

 deficiency in respired oxygen, that is, with 



