144 CHANGES OF AIR AND BLOOD IN RESPIRATION. 



and 1 P. M., having noted the frequency of the pulse and respirations and the 

 exhalation of carbon dioxide at 12 M., he found at 2 p. M., the pulse and res- 

 pirations increased in frequency, the volume of expired air augmented, and 

 the carbon dioxide exhaled increased from 15*77 to 18-22 cubic inches 

 (258-43 to 298-6 c. c.) per minute. In order to ascertain that this variation 

 did not depend upon the time of day, independently of the digestive process, 

 he made a comparison at 12 M., at 1 and at 2 p. M. without taking food, which 

 showed no notable variation, either in the pulse, number of respirations, volume 

 of expired air or quantity of carbon dioxide exhaled. 



The effect of inanition is to gradually diminish the exhalation of carbon 

 dioxide. Bidder and Schmidt noted the daily production in a cat which 

 was subjected to eighteen days of inanition, at the end of which time it died. 

 The quantity diminished gradually from day to day, until just before death 

 it was reduced a little more than one-half. Edward Smith noted in his own 

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

 dimunition in the quantity of air respired, in the quantity of vapor exhaled, 

 in the number of respirations and in the rapidity of the pulse. The exhala- 

 tion of carbon dioxide was diminished one-fourth. An important point in 

 this observation was that the quantity was as small four and a half hours 

 after eating as at the end of the twenty-seven hours. 



Influence of Diet. The most extended series of investigations on the in- 

 fluence of diet upon the absolute quantity of carbon dioxide exhaled are those 

 of Edward Smith. This observer made a large number of experiments 011 

 the influence of various kinds of food, and extended his inquiries into the 

 influence of certain beverages, such as tea, coffee, cocoa, malt liquors and fer- 

 mented liquors. He divided food into two classes : one which increases the 

 exhalation of carbon dioxide, which he called respiratory excitants, and the 

 other, which diminishes the exhalation, he called non-exciters. The follow- 

 ing are the results of a large number of 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 compounds, the vola- 

 tile elements of wines and spirits, and^ coffee-leaves. 



u 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 propor- 

 tion to their quantity. Compound aliments, as the cereals, containing sev- 

 eral of these substances, have an action greater than that of any of their ele- 

 ments. 



" 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 substance containing a large amount of carbon 

 evolves more than a small portion of that carbon in the temporary action 



