376 TEXT-BOOK OF PHYSIOLOGY. 



discharge of carbon dioxid, independent of the increase due to the 

 oxidation of food materials after absorption. It was found that in a 

 fasting man a dose of sodium sulphate increased the absorption of 

 oxygen as much as 17 per cent, and the discharge of CO 2 24 per cent. 

 (Lowy). It is difficult to determine how much of the increase after 

 a meal is therefore due to food oxidation and how much to functional 

 activity of the canal itself. The consumption of nitrogenized 

 meals, however, has a greater effect than non-nitrogenized meals. 



Temperature. A rise in temperature of the surrounding air 

 has as an effect a diminution in the amounts of oxygen consumed and 

 carbon dioxid discharged. A fall in temperature has the opposite 

 effect. Thus a cat at a temperature of 3.2 C. consumed during a 

 period of six hours 21.39 grams of oxygen and discharged 22 grams 

 of carbon dioxid, while at a temperature of 29.6 C. the correspond- 

 ing amounts for the same period of time were for oxygen 13.9 grams 

 and for carbon dioxid 13.12 grams. Lavoisier and Sequin, having 

 reference only to the oxygen, found that a man at a temperature of 

 15 C. consumed 38.31 grams of oxygen, while at a temperature of 

 32.8 C. the corresponding amount was but 35 grams. Similar 

 results have been obtained by other observers with different animals. 

 The explanation of these facts is to be found in the increased activity 

 of all physiologic mechanisms coincident with a fall, and in the 

 decreased activity, coincident with a rise in temperature. Vine lower 

 temperatures act as a stimulus to the peripheral terminations of the 

 nerve system, bringing about reflexly increased activity of the body 

 at large.VThe muscles especially are not only reflexly but volitionally 

 excited to greater activity. This leads naturally to an increase in 

 the consumption of oxygen and in the production of carbon dioxid 

 and in the evolution of heat. 



In cold-blooded animals the respiratory exchange is influenced in 

 a manner the reverse of that observed in warm-blooded animals. 

 With a rise of external temperature and a corresponding rise of 

 body-temperature the discharge of carbon dioxid steadily increases. 

 Thus a frog in an atmosphere at o C. with a body-temperature of 

 I C. discharged per kilogram per hour 4.31 c.c. of carbon dioxid; 

 in an atmosphere of 35 C. with a body-temperature of 34 C. there 

 was discharged 325 c.c. per kilo per hour. Intermediate tempera- 

 tures were attended by corresponding increases in the amounts of 

 UU, discharged. The reason for this difference in the two classes 

 of animals is probably to be found in the want, in the cold-blooded 

 animals, of a self-adjusting heat-regulating mechanism. 



Age.In early youth, as a result partly of the more pronounced 



activity of the nutritive energies and partly of a cutaneous surface 



relatively greater, as compared with the mass of the body, than in 



hfe, the absorption of oxygen and the discharge of carbon 



