EXHALATION OF CARBONIC ACID. 149 



" 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 compounds, the volatile elements 

 of wines and spirits, and coffee-leaves. 



" Respiratory excitants have a temporary action ; but the action of most of them 

 commences very quickly, and attains its maximum within one hour. 



" The most powerful respiratory excitants are tea and sugar ; then coffee, rum, milk, 

 cocoa, ales, and chiccory ; then casein and gluten, and lastly, gelatin and albumen. The 

 amount of action was not in uniform proportion to their quantity. Compound aliments, 

 as the cereals, containing several of these substances, have an action greater than that 

 of any of their elements. 



" Most respiratory excitants, as tea, coffee, gluten, and casein, cause an increase in 

 the evolution of carbon greater than the quantity which they supply, while others, as 

 sugar, supply more than they evolve in this excess, that is, above the basis. No sub- 

 stance containing a large amount of carbon evolves more than a small portion of that 

 carbon in the temporary action occurring above the basis-line, and hence a large portion 

 remains unaccounted for by these experiments." 



The comparative observations of Dr. Smith upon the four persons who were the sub- 

 jects of experiment demonstrated one very important fact ; namely, that the action of 

 different kinds of food upon respiration is modified by idiosyncrasies and the tastes of 

 different individuals. For example, in experiments on his own person, certain articles 

 which were agreeable to him excited the exhalation of carbonic acid ; but in experi- 

 menting with the same articles upon Mr. Moul, to whom they were distasteful, he found 

 the respiratory action diminished. 



Quite a number of observers have noted the influence of alcohol upon the products 

 of respiration ; but the results of experiments have not been entirely uniform. Prout 

 observed a constant diminution in the quantity of carbonic acid exhaled, under the in- 

 fluence of alcohol. This has been confirmed by the observations of Horn, Vierordt, and 

 many others; but Hervier and Saint-Lager assert that the use of alcohol increases the 

 exhalation of carbonic acid. In the experiments of Prout, a small quantity of wine taken 

 fasting caused the proportion of carbonic acid in the expired air to fall immediately 

 from 4 to 3 parts per 100. During the four hours following, it oscillated between 3*40, 

 3*10, and 3. The administration of a second dose, followed by some symptoms of in- 

 toxication, diminished the proportion to 2'70 per 100. Dr. Fyfe, of Edinburgh, showed 

 that the depressing effects of an alcoholic excess were continued into the following day. 

 Dr. Fyfe also noted a fact, important in this connection, namely, that the prolonged use 

 of nitric acid and the condition of the system induced by the administration of mer- 

 curials were attended with a considerable diminution in the daily amount of carbonic 

 acid exhaled by the lungs. In addition, Prout demonstrated that the exhalation of car- 

 bonic acid was diminished by the use of a concentrated infusion of tea, and Horn noted 

 the same effect attending slight narcotism produced by smoking tobacco. 



The observations of Dr. Smith, which were all made fasting, show a certain variation 

 in the effects of different alcoholic beverages. His results are briefly the following : 



" Brandy, whiskey, and gin, and particularly the latter, almost always lessened the 

 respiratory changes recorded, while ruin as commonly increased them. Rum-and-milk 

 had a very pronounced and persistent action, and there was no effect on the sensorium. 

 Ale and porter always increased them, while sherry wine lessened the quantity of air 

 inspired, but slightly increased the carbonic acid evolved. 



"The volatile elements of alcohol, gin, rum, sherry, and port-wine, when inhaled, 

 lessened the quantity of carbonic acid exhaled, and usually lessened the quantity of air 

 inhaled. The effect of fine old port-wine was very decided and uniform ; and it is 

 known that wines and spirits improve in aroma and become weaker in alcohol by age. 

 The excito-respiratory action of rum is probably not due to its volatile elements." 



