CHEMISTRY OF URINE 487 



occasionally observed to mount in health to at least 1036, its persistence 

 at 1025 or 1030 CT anything above this, especially if the urine is pale 

 and apparently dilute, should suggest diabetes mellitus. 



Inorganic Salts. The changes in the quantity of the inorganic con- 

 stituents of the urine in disease are not, in the present state of our 

 knowledge, of as much importance as the changes in the organic con- 

 stituents. The chlorides are diminished in most acute febrile diseases 

 and may even totally disappear from the urine, and their reappearance 

 after the crisis is, so far as it goes, a favourable symptom. In most 

 cases in which the quantity of the urine is markedly lessened, all the 

 inorganic substances are diminished in amount. 



Urea. The quantity of urea is, as a rule, increased in fever, either 

 absolutely or in proportion to the amount of nitrogen in the food. In 

 the interstitial varieties of kidney disease the urea is usually not 

 diminished, but when the stress of the change falls on the tubules 

 (parenchymatous nephritis), it is distinctly decreased it may be even 

 to one-twentieth of the normal. 



Uric acid is diminished in the urine in gout (perhaps to one-ninth of 

 the normal), not only during the paroxysms, but in the intervals. It 

 accumulates in the blood and tissues, and, as sodium urare, may form 

 concretions in the joints, the cartilage of the ear, and other situations. 

 Watson relates the case of a gentleman who used to avail himself of his 

 resources in this respect by scoring the points at cards on the table with 

 his chalky knuckles. In leukaemia the quantity of uric acid and purin 

 bases in the urine is greatly increased, not only absolutely, but also in 

 proportion to the urea. As much as 4^ grammes of free uric acid, in 

 addition to about ij grammes of ammonium urate, has been found in a 

 urinary sediment in a case of leukaemia. 



The aromatic bodies, of which indoxyl may be taken as the type, 

 are increased when the conditions of disease favour the growth of 

 bacteria in the intestine e.g., in cholera, acute peritonitis, and carci- 

 noma of the stomach. A marked increase in the amount of the indican 

 in the urine may, as far as it goes, be taken as an indication that the 

 bacteria are gaining the upper hand in the intestinal tract; a marked 

 diminution is usually a sign that the battle has begun to turn in favour 

 of the organism (Practical Exercises, p. 517). Tryptophane, a sub- 

 stance which we have already recognized among the products of the 

 tryptic digestion of proteins, has been shown to be a precursor of indol, 

 which is formed from it under the influence of bacteria. When trypto- 

 phane is injected into the caecum of rabbits, the indican in the urine 

 is markedly increased. Putrefactive processes in other parts of the 

 body than the intestine may also increase the indican in the urine 

 e.g., a collection of putrid pus in the pleural cavity. 



Abnormal Substances in Urine. Sugar, proteins, the pigments of bile 

 and blood, or their derivatives, are the most important abnormal sub- 

 stances found in solution in the urine. Normal urine, as has been 

 stated, contains a trace of dextrose, but so little that it cannot be 

 detected by ordinary tests, and for practical purposes it may be .con- 

 sidered absent. Dextrose is the sugar found in the urine in diabetes. 

 In the urine of nursing mothers lactose may be present. Pentoses, 

 sugars with five carbon atoms in the molecule (instead of six, as in the 

 hexoses, of which group dextrose is a member), may also occasionally 

 occur in urine. Pentoses give the ordinary reduction tests for sugar, 

 and yield osazones, but do not ferment with yeast. Various plants 

 contain pentoses, and when these are eaten the pentoses are excreted 

 in the urine, but in cases of true pentosuria they originate in the body, 

 possibly from nucleo-proteins. The condition has not the same sinister 

 significance as diabetes. Specific toxic substances produced by bac- 



