426 TEXT-BOOK OF PHYSIOLOGY 



exception of an inlet for air for breathing purposes. The respired air is 

 drawn through a tube and measured by a large meter turned by a water or 

 gas motor. By means of a side tube a fractional quantity of the main 

 column of air is diverted to an absorption apparatus by a small pump. 

 This air first passes into a vessel containing H 2 SO 4 , by which the water is 

 collected; then into long tubes containing barium hydroxid, by which the 

 carbon dioxid is absorbed; thence into a small meter, by which its amount is 

 registered. From the amount of water and carbon dioxid thus obtained 

 the amounts of both in the total air breathed are calculated. The water and 

 carbon dioxid previously present in the air are simultaneously determined by 

 a corresponding absorption apparatus and deducted from the amounts ob- 

 tained from the respired air. As the apparatus is traversed constantly by a 

 column of air of normal composition and the waste products removed as rapidly 

 as discharged, the experiment can be continued for periods varying from 

 six to twenty-four hours without detriment to the subject of the experiment. 



With those forms adapted only for animals Regnault's and Reiset's, or 

 Jolyet and Regnard's it is possible to determine simultaneously the ab- 

 sorption of oxygen and the discharge of carbon dioxid. As the apparatus 

 employed is completely closed, the carbon dioxid must be removed as soon 

 as discharged and the oxygen renewed as soon as absorbed. The former is 

 accomplished by the aspiratory action of moving bulbs containing an alkali, 

 the latter by a steadily acting pressure on a reservoir of oxygen. This 

 apparatus consists essentially of a glass bell-jar in which the animal is 

 placed. This is brought into connection by tubes, on the one hand, with 

 the oxygen reservoir, and, on the other hand, with the aspiratory bulbs, 

 kept in motion by some form of motor. The construction of each of these 

 forms of apparatus is so complex, the conduct of an experiment and the 

 final determination of the results so complicated, that a detailed description 

 would be out of place in a work of this character. 



Of the results obtained by these and other methods a few are given in 

 the following table: 



Oxygen Absorbed. Observer. Carbon Dioxid Discharged. 



746 grams. Vierordt. 876 grams. 



700 grains. Pettenkofer and Voit. 800 grams. 



663 grams. Speck. 770 grams. 



The amounts of oxygen absorbed in Pettenkofer and Voit's experiments 

 varied from 594 to 1072 grams; of carbon dioxid exhaled, from 686 to 1285 

 grams. 



In all these results it is evident on examination that the volume of oxygen 

 absorbed is always greater than the volume of carbon dioxid exhaled, or, 

 what amounts to the same thing, the weight of the oxygen absorbed is always 

 greater than the weight of the oxygen entering into the formation of the 

 carbon dioxid exhaled. The reason for this difference between the amounts 

 of oxygen in the inspired air and in the carbon dioxid exhaled is found in 

 the fact, that on a mixed diet one containing fat a portion of the oxygen 

 is utilized in the oxidation of the surplus hydrogen of the fat with the forma- 

 tion of water. Under such a diet the respiratory quotient is always less 

 than unity, usually 0.916. On a purely carbohydrate diet one in which 

 there is no surplus hydrogen all the oxygen will combine with carbon and 

 be returned as carbon dioxid, and hence the respiratory quotient will be 



