INFLUENCE OF DIET. 435 



the influence of a fast of twenty-seven hours. There was a 

 marked diminution in the quantity of air respired, in the 

 quantity of vapor exhaled, in the nurnher of respirations, and 

 in the rapidity of the pulse. The exhalation of carbonic acid 

 was diminished one-fourth. An interesting point in this 

 observation was the fact that the quantity was as small four 

 and a half hours after eating, as at the end of the twenty- 

 seven hours. " An increase of carbonic acid in the absence 

 of food, at or near the period when it is usually increased by 

 food," was also noted in the experiment of Dr. Smith. 



Influence of Diet. Regnault and Reiset, in their experi- 

 ments on animals, studied the effect of different kinds of diet 

 upon the relations of the quantity of oxygen absorbed to the 

 carbonic acid exhaled. About the only conclusive and ex- 

 tended series of investigations on the influence of diet upon 

 the absolute quantity of carbonic acid exhaled are those 

 of Dr. Smith. This observer made a large number of 

 experiments on the influence of various kinds of food, and 

 extended his inquiries into the influence of certain beverages, 

 such as tea, coffee, cocoa, malt and fermented liquors. 1 We 

 have already fully described the method employed in these 

 experiments, and the conclusions, which are of great interest 

 and importance, are very exact and reliable. 



Dr. Smith divides- food into two classes, one which in- 

 creases the exhalation of carbonic acid, which he calls respi- 

 ratory excitants, and the other, which diminishes the exhala- 

 tion, which he calls non-exciters. 



The following are the results of a large number of care- 

 fully conducted observations upon four persons : 



" The excito-respiratory are nitrogeneous food, milk and 

 its components, sugars, rum, beer, stout, the cereals, and 

 potato. 



" The non-exciters are starch, fat, certain alcoholic com- 



1 On the Action of Foods on the Respiration during the Primary Processes of 

 Digestion. Philosophical Transactions, 1859, p. 715 



