432 Dr. E. Smith on the immediate Source of 



Also that vohmtary increase in the quantity of air inspired, 

 whilst the conditions in which the body is jilaced remain the 

 same, causes increase in the quantity of carbonic acid evolved. 



My own experiments support these statements, and have also 

 shown that whenever food caused an increased elimination of 

 carbonic acid, the respirations were deeper, but not more fre- 

 quent. 



All these have reference to a valuation in the proportion of 

 carbonic acid on the two sides of the capillary membrane. 



2. The action of tea, gluten, and casein, in causing the 

 evolution of more carbon than they supply, and of the cereals 

 and sugar in causing the elimination of only a small part of their 

 carbon during this period of increase, agrees with this theory; 

 for this indirect or intermediate action is independent of the car- 

 bon contained in the aliment, and may therefore bear no definite 

 proportion to it. Indeed, as has been shown above, starch and 

 fat, so rich in carbon, are almost inert in reference to this increase 

 in the evolution of carbon. 



3. The fact that this effect does not increase pari passti with 

 increase in the dose, supports the theory of this indirect action. 

 Thus tea, gluten, and casein act as well in a moderately small 

 dose as in larger ones; indeed, in reference to tea it was proved 

 that, whilst 50 grains caused a large evolution, 100 grs. seldom 

 caused a larger, and 150 grs. often induced a smaller evolution 

 than that resulting from 50 grs. A certain quantity of one of 

 these substances being present at a given moment, the effect is 

 not proportionately greater from a larger dose. 



4. A repetition of small doses has much greater effect than 

 the administration of the amount of a number of small doses 

 given at once. Thus 150 grs. of tea caused a total increase in 

 a given time of from 50 to 60 grs. of carbonic acid ; but 6 doses 

 of 25 grs. each, given at intervals of a quarter of an hour in the 

 same time, caused the evolution of 200 grs. of carbonic acid. 

 This quality is known to exist in various drugs. 



5. The rapidity of the action of substances comports the best 

 with this theory. Thus Hoz. of sugar dissolved in water will 

 cause an increase of 1 gr. of carbonic acid per minute in less than 

 10 minutes, and a maximum increase of 2| grs. in 27 minutes, 

 after which period there is a rapid subsidence. It is true that 

 by reagents wc may transform one kind of sugar into another 

 kind in an instant, and may convert starch into dextrine in a 

 very short period; still there are no facts which warrant the 

 belief in so rapid a resolution of sugar into carbonic acid as 

 that just given. On the theory under discussion, however, the 

 rapidity observed, in the increased evolution of carbonic acid 

 oflPers no objection. 



