liebig's organic chemistry. 
187 
adult, is estimated by different authors at from 746 to 837 
pounds in a year; yet the increase, or variation of weight, 
in an individual amounts only to a few pounds. What, then, 
has become of this large amount of matter? An examina- 
tion of the products given out from the body during the same 
period, affords a satisfactory elucidation of this question. 
Carbonic acid and water, both requiring oxygen for their 
formation, are constantly separated from the system, and in 
amounts proportionate to the oxygen which disappears. 
For, " if we assume, with Lavoisier and Seuguin, in order 
to obtain a foundation for our calculation, that an adult man 
receives into his system, daily, 32.5 oz. of oxygen, and that 
the weight of the whole mass of his blood, of which 80 per 
cent, is water, is 24 lbs.: it then appears, from the known 
composition of the blood, that, in order to convert the whole 
of its carbon ana* hydrogen into carbonic acid and water, 
64.103 grs. of oxygen will be required. This quantity will 
be taken into the system of an adult in four days and five 
hours." 
It has been determined, by observation, that an adult 
consumes the average daily amount of 13.9 oz. of carbon, 
after deducting from the whole amount of ingesta that por- 
tion which passes off as the refuse of the system, and in the 
form of secretions unaffected by the absorbed oxygen. The 
whole of this must escape from the lungs as carbonic acid, 
requiring, to effect this, 37. oz. of oxygen. The oxygen 
taken into the system is found in no other form or com- 
bination than with carbon or hydrogen; and, as the carbon, 
and hydrogen carried off is replaced by the same elements 
from the food, a direct ratio is immediately established be- 
tween the amount of oxygen respired and the food consumed. 
This is illustrated by the fact, that those circumstances, either 
natural or artificial, which cause a variation in the number 
of respirations, also produce a difference in the amount of 
ingesta necessary for the support of the vital action, of which 
