240 THE URINE. 



will also decrease ; and if the amount of food then remains constant, 

 the nitrogenous output will likewise remain the same. If, on the 

 other hand, more nitrogen is now ingested, an increased elimination 

 will result ; but a certain fraction is retained by the body and grad- 

 ually a higher level of equilibrium becomes established. 



There are natural limits to this power of accommodation, how- 

 ever, and we finally reach a point which varies in different indi- 

 viduals, where a further increase in the amount of nitrogen that is 

 ingested does not lead to a higher level of equilibrium, and where 

 consequently a further retention of nitrogen does not occur. 



From the fact that the level of nitrogenous equilibrium is different 

 in different people and may vary in one and the same individual, it 

 follows that the amount of urea also must vary. Any figures indi- 

 cating the amount of urea that is eliminated in the urine can there- 

 fore be of little value unless we are acquainted with the actual state 

 of health of the individual, his body-weight, his habits of life as 

 regards exercise, the amount of nitrogenous food ingested, etc. 

 Having a knowledge of all these factors, however, we may be able 

 to say whether the amount of urea is normal or not. Certain figures 

 have been given by physiologists to indicate the amount of nitrogen- 

 ous food which should enter into the composition of the diet, and 

 from these we can approximately calculate the amount of urea that 

 should appear in the urine. By estimating this in turn, or still 

 better, of course, the total amount of nitrogen, we can accordingly 

 decide whether or not the individual is consuming a sufficient amount 

 of nitrogen in his food. The older figures, however, have been 

 constructed without due regard to the factors above indicated, and 

 are, in my opinion at least, too high as averages. This is now 

 realized more generally, and the figures given by Chittenden and 

 Folin, for example, are decidedly low. The latter thus gives about 

 120 grammes of albumin, 150 grammes of fat, and 225 grammes 

 of carbohydrate. 



I am willing to admit that an elimination of 40 to 50 grammes of 

 urea may be normal in certain cases, as in soldiers on forced marches, 

 among the laboring classes, etc., but I should certainly look upon 

 the average merchant or student who leads a sedentary life as an 

 overfed individual if his daily elimination of urea should exceed 

 30 grammes in the twenty-four hours. Among the well-to-do classes 

 I find that an elimination of from 20 to 25 grammes is probably 

 normal, taking the body-weight of the person into consideration. 

 A smaller amount even is not infrequently met with in individuals 

 of sedentary habits who are in perfect health, but I should scarcely 

 regard such a quantity as normal for the average laboring-man. 

 While extensive variations in the amount of urea are thus observed 

 in health, still greater deviations from average figures are noted in 

 disease, but here as there we must always take into account the 

 amount of nitrogen that is ingested and the body weight. 



