Only two other properties of the urine in fasting may be discussed in this place; of these the former commands more theoretical, the latter more practical, interest.

a. The Urinary Ammonia

The Urinary Ammonia increases in fasting while the urea becomes correspondingly decreased. The absolute volume of the ammonia excretion also rises. This is attributable to the great production of acids that occurs in a fasting organism. In addition to sulphuric acid and phosphoric acid that are liberated from the proteids of the body, diacetic and oxybutyric acid also materially contribute to the increased acidulation. In any case of high acetonuria one can count upon finding high values for urinary ammonia and vice versa. It is essential, of course, that the urine examined should be fresh, as it will otherwise contain a certain amount of ammonia that is derived from the bacterial decomposition of urea after the urine was voided. Within the organism the acids combine with ammonia and by binding it in this way prevent its transformation into urea. The following example may illustrate the values that may be obtained:

table 3

In chronic undernutrition an increase of the urinary ammonia is only found in the presence of acetonuria (see above).

b. The Urinary Chlorides (Sodium Chloride)

The Urinary Chlorides (Sodium Chloride) excretion becomes reduced during fasting to very low values. The depth of the excretion will depend principally upon the amount of sodium chloride that was ingested prior to the period of fasting. A certain time is required by the organism to get rid of surplus sodium chloride that may have accumulated. On the second, and, at the latest, by the third day of complete fasting, however, the urine rarely contains more than 1 g of sodium chloride in the total 24 hours' excretion, and after the fifth day of fasting rarely more than

0.6 g. This is diagnostically important. Every physician has, no doubt, heard patients declare falsely that for so and so long they had not eaten any food whatsoever. If in such cases the urine gives an abundant chloride precipitate with silver nitrate and if upon quantitative analysis several grams of sodium chloride are found in the 24 hours' quantity, then these findings may be considered valuable evidence towards disproving the veracity of the patient's statements.

In chronic undernutrition the excretion of sodium chloride also, of course, becomes reduced. No general rules can, however, be formulated in regard to the degree of this deficit, for everything will depend, not alone upon the quantity, but upon the quality of the food as well. Relatively the greatest decrease in the urinary chloride excretion in undernutrition is seen if, as is so frequently the case, milk alone is taken; for 2 liters of milk (representing about 1250 calories) contain only from 3 to 3.2 g of sodium chloride; and about this amount of chlorides are reclaimed from the urine in such individuals if this same diet is persisted in for some length of time.