432 METABOLIC EQUILIBRIUM. 



The relative amount of nitrogen and carbon in albumin may be expressed 

 as i : 3.3. Of the amount of carbon decomposed in the process of metabolism 

 there are 3.3 parts for every part of nitrogen in the proteids subjected to the 

 process. The excess is to be attributed to the decomposition of non-nitrogenous 

 substances (fats or carbohydrates). 



It is believed that the greater portion of the 'proteids are decomposed 

 in the tissues into carbamic acid, which is then transformed in large amounts, 

 in the liver, into urea. 



The excretion of nitrogen after the taking of food is, in animals, not 

 uniform from hour to hour, but it increases rapidly at once, reaches its maxi- 

 mum after 5 or 6 hours and then gradually declines. The excretion of sulphur 

 and phosphorus pursues a similar course, though the maximum excretion, on 

 a meat diet, occurs as early as the fourth hour. On addition of fat to a meat- 

 diet the excretion of nitrogen and of sulphur is more evenly distributed through- 

 out the hours of the day. In human beings Rosemann found during the day 

 an increase between 9 and n a. m., as a result of breakfast and the stimu- 

 lation of all of the functions in the morning; a second increase between 3 and 

 4 p. m., as a result of dinner; a third, smaller one between 7 and 9 p. m., fol- 

 lowing supper; and a final increase between 9 and n p. m. The excretion 

 diminishes during the night. 



The nitrogenous constituents of the body become poorer in carbon as 

 a result of the processes of metabolism, but richer in nitrogen and oxygen ; 

 for there are, in the albumins, 4 atoms of carbon for each atom of nitrogen, 

 in gelatin 3^ atoms of carbon, in glycocoll 2 of carbon, in kreatin i^ of carbon, 

 in uric acid i of carbon, in allantoin i of carbon, in urea, finally, only \ atom 

 of carbon. 



The oxygen furnished by respiration is either determined directly from 

 the reduction in its amount in the air supplied to the animal, or it is calculated 

 from other data. This inspired oxygen, as well as the oxygen of the food, 

 makes its appearance principally in the form of carbon dioxid and water; 

 a small amount leaves the body in the excrementitious products. The amount 

 of oxygen absorbed in respiration is the measure of the entire process of 

 combustion in the body, by which carbon is oxidized into carbon dioxid and 

 hydrogen into water. The respiratory quotient indicates the amount of 

 inspired oxygen that is required alone for the combustion of the carbon. 

 If the volume of carbon dioxid produced by the combustion of pure carbon 

 is exactly the same as the volume of oxygen consumed for this purpose, the 

 respiratory quotient is i. This is the case in the decomposition of carbo- 

 hydrates. As hydrogen and oxygen are present in these compounds in the 

 proportion necessary to form water by combustion, practically all the oxygen 

 is utilized for the oxidation of the carbon of the carbohydrates. For albumin 

 the respiratory quotient is 0.8, for, on a purely albuminous diet, only 800 cu. 

 cm. of carbon dioxid are excreted for every 1000 cu. cm. of oxygen. For 

 fats the respiratory quotient is 0.7, for, on a diet of fat, only 700 cu. cm. of 

 carbon dioxid are excreted for every 1000 cu. cm. of oxygen consumed. Thus 

 for fats and albumin the respiratory quotient is smaller than for carbohydrates, 

 the volume of carbon dioxid excreted is less than that of oxygen inspired, 

 because in the combustion of albumin or fat a part of the oxygen taken up 

 must be employed for the oxidation of hydrogen into water. 



In case a larger volume of carbon dioxid is excreted than the amount of 

 oxygen absorbed, the respiratory quotient rises above i. This happens 

 if, in addition to the inspired oxygen, a portion of the oxygen from the con- 

 stituents of the food is converted into carbon dioxid in the process of com- 

 bustion in the body. This is the case, for example, when nutritive materials 

 rich in oxygen (for example, carbohydrates) are transformed in the body into 

 those poor in oxygen (for example, fats). 



The respiratory quotient may also, under certain circumstances, become 

 even smaller than it is after an exclusive fat-diet, if, for instance, a portion 

 of the inspired oxygen is employed in the body for the formation and deposi- 

 tion in the tissues of compounds rich in oxygen (for example, in the formation 

 of glycogen) . ^ 



The respiratory quotient may, however, exhibit certain periodic varia- 

 tions independently of the character of the diet. As the oxygen taken up 

 is not always used in the formation of carbon dioxid immediately upon its 

 entrance into the body, but as certain intermediate predecessors of carbon 

 dioxid, rich in oxygen, may accumulate in the body and be excreted only 



