264 



RESPIRATION 



amount seems to be a trifle too great, since from the average of many inves- 

 tigations the total amount of carbon dioxide excreted per day by the entire 

 body has been found to be about 400 liters, weighing 800 grams, and con- 

 sisting of 218 grams of carbon, and 582 grams of oxygen. From the 218 

 grams of carbon must be deducted about 10 grams excreted in other ways 



FIG. 236. Apparatus for Estimating O a and CO 2 in Expired Air. (Waller.) 



than by the lungs, which leaves about 215 grams as the amount of carbon ex- 

 creted by the average healthy man by respiration each day and night. These 

 quantities must be considered approximate only, inasmuch as various cir- 

 cumstances, even in health, influence the amount of carbon dioxide excreted, 

 and, correlatively, the amount of oxygen absorbed. 



Circumstances Influencing the Amount of Carbon Dioxide Excreted. Age and Sex. 

 The quantity of carbon dioxide exhaled into the air breathed by males, regularly in- 

 creases from 8 to 30 years of age; from 30 to 50 the quantity, after remaining stationary for 

 a while, gradually diminishes, and from 50 to extreme age it goes on diminishing, till it 

 scarcely exceeds the quantity exhaled at 10 years old. In females (in whom the quantity 

 exhaled is always less than in males of the same age) the same regular increase in quantity 

 goes on from the 8th year to the age of puberty, when the quantity abruptly ceases to in- 

 crease, and remains stationary so long as they continue to menstruate. When menstrua- 

 tion has ceased, the carbon dioxide output soon decreases at the same rate as it does in 

 old men. 



