344 RESPIRATION 



less than 1, and with ordinary food may be estimated at about 0.8. When 

 fat is being formed from carbohydrates and being stored the respiratory 

 quotient may exceed 1. 



Reduced to dryness and to the expired air, therefore, has a smaller 



10 12 2 4 

 a.m. p.m. 



FIG. 135.^ The elimination of carbon dioxide: - on ordinary diet (mean for three 



days) ; and while fasting (mean for five days) . All the determinations were 



made on the same individual, a man twenty-five years old. On the food days he slept 

 between 12 o'clock midnight and 6 A.M. On the fasting days he slept between 10 P.M. 

 and 6 A.M. 



volume than the inspired air. Measured directly its volume is greater because 

 of its water vapor and higher temperature. 



For example, let us suppose that the inspired air (500 c.c.) has a tempera- 

 ture of 20 C., and that it is saturated with water vapor at this temperature 

 (tension 17.4 mm. Hg.). Expired air, we will suppose, has a temperature of 

 37.5 C., is saturated with water vapor (tension at this temperature 47 mm. Hg.) 

 has lost 4.783 per cent oxygen and has gained 4.380 per cent carbon dioxide. 

 Measured directly then the expired air would have a volume of 554.89 c.c. i. e., 

 approximately one-ninth greater than inspired air. The difference would evi- 

 dently be greater the colder the inspired air (J. R. Ewald). 



During recent years the question whether the expired air contains poison- 

 ous gaseous constituents has been very actively discussed. Brown- Sequard 



