434 Dr. E. Smith on the immediate Source of 



there is a larger increase iu tlie quantity of carbonic acid evolved 

 in cold than in hot weather, but not in a definite relation to the 

 degrees of heat. Thus at a medium temperature of 55° to 60° 

 F. there is no relation between the temperature and the carbonic 

 acid ; with higher and lower temperatures the relations of the 

 carbonic acid are inverse, but so that sudden and violent changes 

 have the greatest effect soon after the long continuance of the 

 opposite condition, and after prolonged heat the carbonic acid 

 still declines for a time after the temperature has begun to decline. 

 The influence of temperature is next to that of exertion in point 

 of duration and power, but the precise mode in which it acts is 

 not yet made known. 



3. The relation between the quantity of carbonic acid and 

 nitrogen evolved at the same period and under the same influences 

 point to this theory. It is known that with exertion there is 

 this relation in reference to the carbon and nitrogen. Barral 

 has shown that it exists in reference to season ; and I have proved 

 that it occurs in the action of tea. It is highly probable that 

 its existence is univei'sal, but not in a constant proportion. This 

 points to the tissues of the body as the immediate source of both. 



4. The variation in the weight of the body due to the action 

 of certain nitrogenous substances, as tea, for example, has re- 

 ference to this theory. Thus at the Wakefield Convict Prison 

 it was found that the addition of a pint of tea daily to the dietary, 

 as well as the substitution of tea for gruel, both alike caused a 

 loss of weight in the prisoners ; and tea, as has just been shown, 

 increases the elimination of both carbon and nitrogen pari passu, 

 and in a quantity greater than it supplies. 



Such are some of the facts which have occurred to me in the 

 course of some thousands of experiments. To these might be 

 added others, as, for example, statements by Andral and Gavarret 

 and others, in reference to the quantity of carbonic acid exhaled 

 at different ages, which tend to show that the relation between 

 the carbon and nitrogen excreted is maintained through life, 

 proceeds somewhat pari passu with the amount of food taken, 

 and is in relation to the activity and extent of the vital changes 

 at different periods of life. 



Hence, on a review of the foregoing, we may conclude : — 



1. That although there may be an increase in the quantity of 

 carbonic acid evolved after the introduction of food into the 

 system, and that increase pursue a definite course, it is not de- 

 rived from the carbon which was contained in the food taken 

 immediately antecedent to it. 



2. All foods, whatever may be their constitution, produce this 

 increase by an indirect influence, and before their own transform- 

 ations are completed. 



