546 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



The quotient is lowered by an animal diet and increased by a vegetable diet, 

 the ratio approximating unity if the diet be sufficiently rich in carbohydrates. 

 Hanriot and Richet l in observations on man noted that before feeding the quo- 

 tient was 0.84 to 0.89 ; when meat or fat was given the consumption of O was 

 increased, but there was no increase in CO 2 , and the quotient fell to 0.76 ; when 

 given potatoes it was 0.93 ; and when the diet was of glucose it reached 1.03. 

 During fasting the quotient falls rapidly. The experiments of Zuntz and 

 Lehmann 2 show that in dogs it falls as low as 0.65 to 0.68 on the second day 

 of fasting, and that on the resumption of food it rises to 0.73 to 0.81. 



The influence of age is manifest in the fact that in children the quotient is 

 lower than in the adult, more O being absorbed in proportion to the CO 2 given 

 off than after full growth has been reached. 



The quotient undergoes a diurnal variation. The day-time is more favor- 

 able than the night for the discharge of CO 2 , as well as for the absorption of 

 O, owing mainly to greater muscular activity during the day, but the CO 3 

 is more affected than the O ; hence the respiratory quotient is higher during 

 the day. In the recent experiments by Saint-Martin 3 on birds, the mean quo- 

 tient during the day was 0.83 and during the night 0.72 ; the ratio for CO 2 

 for the day and night was 1 : 0.78, and for O 1 : 0.9. During the night the 

 elimination of CO 2 was diminished about 20 per cent., while the absorption of 

 O fell only about 10 per cent. 



The quotient is increased by a rise of external temperature. Thus, Pfliiger 

 and Finkler found in guinea-pigs that the quotient was 0.83 at 3.64 and 0.94 

 at 26.21. When the bodily temperature is increased, as in fever, the respira- 

 tory quotient remains practically unaltered. When the temperature falls below 

 the normal the respiratory quotient increases. 



Muscular activity is also an important factor. During rest the consumption 

 of O by muscles is greater than the production of CO 2 , while during contrac- 

 tion the difference becomes less and less in proportion to the degree of activity, 

 until finally more CO 2 may be given off than there is O consumed. Sczelkow 

 found in experiments on muscles of rabbits at rest and in tetanus that the 

 respiratory quotient was decidedly increased. A mean of six experiments 

 gives as the quotient during rest 0.543 and during tetanus 0.933 ; in one-half 

 of the experiments it went above 1, and in one instance to 1.13. 



During sleep the output of CO 2 is diminished more than the consumption 

 of O (p. 542), so that the respiratory quotient is less than when awake and 

 quiet. 



During hybernation the quotient falls to a minimum in the marmot as low 

 as 0.49. This is due chiefly to the more decided falling off in the quantity of 

 CO 2 , the CO 2 being reduced to -fa, and the O to only ^ ; the animal, however, 

 is not only in a state of muscular quiet, but fasting, which, it will be remem- 

 bered, is an important factor in lowering the quotient. 



1 Compt. rend., 1888, vol. 106, pp. 496-498. 



2 Berliner klin. Woch., 1887, p. 428. 



3 Compt. rend., 1887, vol. 105, pp. 1124-1128. 



