4 86 EXCRETION 



taking place in the kidney, and upon the general problems of metabolism. 

 Even in health the quantity of the urine, its specific gravity, its acidity, 

 may vary within wide limits. A hot day may increase the secretion 

 of sweat, and correspondingly diminish the secretion of urine, and the 

 deficiency of water may lead to a deposit of brick-red urates. A meal 

 rich in fruit or vegetables may render the urine alkaline, and its alkalinity 

 may determine a precipitate of earthy phosphates. But neither the 

 scanty acid urine with its sediment of urates, nor the alkaline urine 

 with its sediment of phosphates, somes into the category of pathological 

 urines; the deviation from the normal does not amount to disease. 

 The maximum deviation from the line of health is the total suppression 

 of the urine. If this lasts long, a train of symptoms, oi which con- 

 vulsions may be one of the most prominent, and which are grouped 

 under the name of uraemia, appears. At length the patient becomes 

 comatose, and death closes the scene. Suppression of urine may be 

 the consequence of many pathological conditions, but there is one case 

 on record in the human subject which, in effect, though not in intention, 

 belongs to experimental physiology. A surgeon diagnosed a floating 

 kidney in a woman. With a natural impatience of loose odds and 

 ends of this sort, he offered to remove it, and in an evil hour the patient 

 consented. The surgeon, a perfectly skilful man, who acted for the 

 best, and to whom no blame whatever attached, carried the kidney to 

 a well-known pathologist for examination. The latter, to the horror 

 of the operator, suggested, from the appearance of the organ, that it 

 was the only kidney the woman possessed. This turned out to be the 

 fact. Not a drop of urine was passed. Apart from this ominous 

 symptom, all went well for seven or eight days; but then uraemic 

 troubles came on, and the patient died on the eleventh or thirteenth 

 day after the operation. The necropsy showed that her only kidney 

 had been taken away. 



In disease the urine may contain abnormal constituents, or ordinary 

 constituents in abnormal amounts. Of the normal constituents which 

 may be altered in quantity, the most important are the water, the inor- 

 ganic salts, the urea, the uric acid, and the aromatic substances. 



Water. A marked and persistent diminution in the quantity of 

 urine that is to say, practically in the water, with or without an 

 increase in the specific gravity is suggestive of disorganization of the 

 renal epithelium. In some infective diseases the kidney is liable to 

 be secondarily involved, its secreting cells being perhaps crippled in the 

 attempt to eliminate the bacterial poisons. In the form of paren- 

 chymatous or tubal nephritis which so frequently complicates scarlet 

 fever, the quantity of urine has in some cases fallen to 50 or 60 c.c. in 

 the twenty-four hours. 



In chronic interstitial nephritis (' granular kidney '), on the other 

 hand, where the structural changes in the tubules are, for a long time 

 at least, comparatively circumscribed, the quantity of urine is often 

 increased and of low specific gravity. In these cases the increase in 

 the blood-pressure, associated with hypertrophy of the heart, may be 

 a factor in the exaggerated renal secretion. In diabetes mellitus the 

 quantity of urine is greatly increased, perhaps in some cases because 

 more urea is excreted than normal, and urea acts as a diuretic, perhaps 

 also because the elimination of sugar draws with it an increased excretion 

 of water to hold it in solution. Although a specific gravity as low as 

 1002 has been seen in healthy persons (after copious potations), the 

 persistence of a density below 1010 should suggest hydruria. Watson 

 mentions the case of a boy with diabetes insipid us, who voided in 

 twenty-four hours 9 or 10 pints (5 to 6 litres) of urine with a specific 

 gravity of 1002. On the other hand, while the specific gravity has been 



