A CTIVITY OF THE ALIMENTAR Y CANAL. 7 1 9 



fast the absorption of oxygen and the discharge of carbon dioxide were 

 4'67 c.c. and 3*16 c.c. per kilo, and minute ; after this meal the 

 figures were respectively 5'05 c.c. and 346 c.c. The effects of the fast 

 and of food upon the respiratory quotient were as follows : 



CO 



On last day of food, mixed diet . . -^ = 0'73 



^2 

 On second day of fasting . . . . 68 



On third day of fasting . . , ,, 0'65 



During the remainder of the fast . 0'66-0'68 



When food, mixed diet, was again taken . ,, 0*73-0 '81 



Eegarding the influence of diet upon the respiratory quotient, it is 

 only necessary here to state that an animal fed on a vegetable diet has a 

 quotient closely approaching unity, for its chief food, the carbohydrates, 

 contains enough oxygen to combine with the hydrogen to form water ; 

 that a carnivorous animal has a quotient about 074, and an omnivorous 

 animal, such as man, a somewhat higher quotient l ; and finally, that 

 even a herbivorous animal has a low quotient during starvation, for it 

 then lives upon its own tissues. 



The influence of activity of the alimentary canal upon the 

 respiratory exchange. It has already been shown that a meal 

 increases the respiratory exchange, and this effect was originally attri- 

 buted solely to the oxidation of the food material taken up by the 

 blood. Speck,' 2 however, in 1874, pointed out that this increase in 

 metabolism followed the taking of food so rapidly that it appeared to be 

 due, in the first place, to the augmented activity of the alimentary canal. 

 The first experiments to support this view were those made by Mering 

 and Zuntz, 3 who showed that food placed in the stomach increased the 

 absorption of oxygen and the discharge of carbon dioxide, whereas sub- 

 stances such as lactic acid, butyric acid, glycerin, sugar, egg albumin, and 

 peptone, injected into the blood, increased the output of carbon dioxide, but 

 had no marked effect upon the intake of oxygen. Eubner 4 and Fredericq 5 

 also found increased metabolism after food, due apparently, in the first 

 place, to the activity of the glands of the alimentary canal ; 6 and the 

 observations made by Lehmann and Zuntz T upon the fasting-man 

 Cetti showed that during the fast the respiratory exchange was 

 constant, except on two days when Cetti suffered from colic ; there 

 was then an increase in the intake of oxygen and the output of carbon 

 dioxide. These pieces of evidence have been followed up by Lowy, 8 

 who determined the respiratory exchange of fasting men before and 

 after the activity of the alimentary canal had been increased by a dose 

 of sodium sulphate, or a draught of cold water. Experiments made 

 upon six men showed that the increased activity of the alimentary canal 

 brought about in this way increased the intake of oxygen and the 

 output of carbon dioxide by about 10 per cent. ; the greatest increase 



1 See tables on pp. 706-708. 



2 Arch.f. e'xper. Path. u. Pharm., Leipzig, 1874, Bd. ii. 



3 Arch.f. d. ges. PhysioL, Bonn, 1877, Bd. xv. S. 634 ; 1883, Bd. xxxii. S. 173. 



4 Ztschr.f. BioL, Munchen, 1883, Bd. xix. S. 330. 



5 Arch, de biol., Gand, 1882, tome iv. p. 433. 



6 See also Slosse, Arch. f. Phy.noL, Leipzig, 1890, Suppl. Bd. S. 164 ; Tangl, ibid., 

 1894, S. 283. 



7 Berl. Tclin. Wchnxchr., 1887, S. 428. 



8 Arch. f. d. ges. PhysioL, Bonn, 1888, Bd. xliii. S. 515. 



