258 CONDITIONS INFLUENCING THE EXCRETION OF C0 2 . 



39C. excreted three times as much C0 2 as when the temperature was 

 6C. (Moleschott). 



Warm-Uooded animals behave somewhat differently when the temper- 

 ature of the surrounding medium is changed. When the temperature 

 of the animal is lowered thereby, there is a considerable decrease in the 

 amount of C0 2 given off, as in cold-blooded animals ; but if the temper- 

 ature of the animal be increased (also in fever), the C0 2 is increased 

 (C. Ludwig and Sanders-Ezn). Exactly the reverse obtains when the 

 temperature of the surroundings varies, and the bodily temperature 

 remains constant. As the cold of the surrounding medium increases, 

 the processes of oxidation within the body are increased through some 

 as yet unknown reflex mechanism; the number and depth of the 

 respirations increase, whereby more is taken in and more C0 2 is given 

 out (Lavoisier). A man in January uses 3 2 '2 grammes per hour; in 

 July only 31 '7 grammes. In animals, with the temperature of the 

 surroundings at 8C., the C0 2 given off was one-third greater than with 

 a temperature of 38C. When the temperature of the air increases 

 the body temperature remaining the same the respiratory activity and 

 the C0 2 given off diminish, while the pulse remains nearly constant 

 (Vierordt). On passing suddenly from a cold to a warm medium the 

 amount of C0 2 is considerably diminished ; and conversely, on passing 

 from a warm to a cold medium, the amount is considerably increased 

 (compare Regulation of Temperature). 



6. Muscular exercise causes a considerable increase in the C0 2 given 

 out (Scharling), which may be three times greater during walking than 

 during rest (Ed. Smith). Ludwig and Sczelkow estimated the taken 

 in and the C0 2 given off by a rabbit during rest, and when the muscles 

 of the hind limbs were tetanised. During tetanus the and C0 2 were 

 increased considerably, but in tetanised animals more O was given 

 off in the C0 2 expired than was taken up simultaneously during respira- 

 tion. The passive animal absorbed nearly twice as much O as the 

 amount of C0 2 given off (compare Metabolism in Muscle). 



7. Taking of food causes constantly a not inconsiderable increase in 

 the C0 2 given off, which depends upon the quantity taken, and the 

 increase generally occurs about an hour after the chief meal dinner 

 (Vierordt). During inanition, the exchange of gases diminishes con- 

 siderably until death occurs (Letellier). At first the C0 2 given off 

 diminishes more quickly than the is taken up. The quality of the food 

 influences the C0 2 given off to this extent, that substances rich in carbon 

 (carbohydrates and fats) cause a greater excretion of C0 2 than substances 

 which contain less C (albumins). Eegnault and Eeiset found that a dog 

 gave off 79 per cent, of the O inspired after a flesh diet, and 91 per cent, 

 after a diet of starch. If easily oxidisable substances (glycerine or 



