641 



nearly all nitrogenous foods, and is almost entirely composed of these 

 substances. 



The non-excitants are starch, fat, some alcohols, and coffee-leaves, 



The respiratory excitants are sugar, milk, the cereals, potato, tea, 

 coffee, chichory, cocoa, alcohol, rum, ales, some wines, gluten, casein, 

 gelatin, fibrin, and albumen. 



Of the hydrocarbons, sugar acted very differently from starch and 

 fat. 



All the " respiratory excitants " increased the depth, but not the 

 rate of respiration. 



Some of them acted with great rapidity ; as, for example, sugar 

 and tea, which sometimes caused an increase of 1 grain of carbonic 

 acid per minute in from five to eight minutes. Others, as gluten 

 and casein, acted with less rapidity. In many, as tea and gluten, 

 there was not a proportionate increase in the carbonic acid with in- 

 crease in the quantity of the "excitant." Some of them, as tea, 

 produced much greater effect when a small dose was frequently 

 repeated, than when the whole quantity was given at once, and 

 caused a much greater evolution of carbon than they supplied. The 

 duration of the increase was very different with different foods, but 

 that with sugar was the least, and then that with tea, while that 

 with the cereals and rum and milk was the greatest. The amount 

 of carbonic acid progressively increased at each examination until 

 the maximum was attained ; after which it remained nearly sta- 

 tionary for some time, as with the cereals, or subsided rapidly to the 

 basis quantity, as with sugar. 



The paper was illustrated by a series of diagrams, and accom- 

 panied by tables. 



