^2 EXCRETION 



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 i 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 increasein 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. 510). 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- 

 terial action have been demonstrated in the urine in certain diseases. 

 Red blood-corpuscles and leucocytes (pus corpuscles, white blood- 

 corpuscles, mucous corpuscles) are the chief organized deposits; but 

 spermatozoa may occasionally be found, as well as pathogenic bacteria 

 e.g., the typhoid bacillus; and in disease of the kidney casts of the renal 

 tubules are not uncommon. These tube-casts may be composed chiefly 

 of red blood -corpuscles, or of leucocytes, or of the epithelium of the 

 tubules, sometimes fattily degenerated, or of structureless protein, 

 Dr of amyloid substance. Abnormal crystalline substances, such as 

 the ammo-acids, leucin (Fig. 186), tyrosin (Fig. 187), and cystin 

 (Fig. 1 80), may be on rare occasions found in urinary sediments; but 

 generally the unorganized deposits of pathological urine consist of 

 bodies actually contained in, or obtainable from, the normal secretion, 

 but present in excess, either absolutely, or relatively to the solvent 

 power of the urine. Cystin is of interest because of its relations to the 

 sulphur of the protein molecule (p. 354). It is not found in the normal 

 organism. It very occasionally forms calculi in the bladder. There 

 are individuals who constantly pass as much as one-fourth of all the 

 sulphur in the form of cystin, without any other symptoms. 



