34 DISCHARGE OF CARBON. 



nitrogen discharged, and of oxygen taken in daily, by 

 the organism, when the body-weight is constant. 



The Discharge of Carbon. 



' The influence of food on the rate of discharge of CO 2 is 

 direct and immediate. The increase after each meal, 

 which may amount to 20 per cent, reaches its maximum 

 in about 2 hours. The effect is most marked when the 

 diet consists largely of carbohydrates. 



About 95 per cent, of the carbon discharged leaves the 

 organism as CO 2 , and forms part of the "insensible loss," 

 that is, the loss of weight of the body when no food is 

 taken and no liquid or solid excreta are discharged. The 

 insensible loss is made up of the sum of the CO 2 and 

 water discharged, minus the weight of oxygen absorbed. 

 In man it amounts to about 25 grammes per 'hour. 



Of the total hourly discharge of CO 2 less than half per 

 cent is cutaneous. The hourly discharge of CO 2 by 

 weight of an adult male when at rest, is about 32 grammes, 

 the weight of oxygen absorbed in the same time being 

 from 25 to 28 grammes. The hourly discharge of water 

 vapour is about 20 grammes. 



As a volume of CO 2 contains the same weight of O as 

 an equal volume of O, it is obvious that if all the inspired 

 O were discharged as CO 2 , the quotient (by volume) called 

 the " Respiratory Quotient " ^ would be = I. This, 

 however, is never the case. The volume of O absorbed 

 exceeds very considerably that of the CO 2 discharge, the 

 ratio between them being determined by the composition 

 of the food. In animals which feed exclusively upon 

 carbohydrates, equality is approached. The excess of 

 oxygen is greatest when the diet consists largely of fats. 



On a mixed diet comprising 100 grammes of proteid, 100 grammes of fat, 

 and 250 grammes of carbohydrates (see Table I. ), with a CO 2 discharge of 

 770 grammes daily, the assumption of O by the organism amounts to 666 



