448 A MANUAL OF PHYSIOLOGY 



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, sug- 

 gested, 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 ursemic 

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

 thirteenth day after the operation. The autopsy 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 im- 

 portant are the water, the inorganic 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 with- 

 out an increase in the specific gravity is suggestive of disorgani- 

 zation 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 parenchymatous 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 hyper- 

 trophy 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 joio should suggest hydruria. 

 Watson mentions the case of a boy with diabetes insipidus, 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 occasionally observed to mount in health 

 to at least 1036, its persistence at 1025 or 1030 or anything 

 above this, especially if the urine is pale and apparently dilute, 

 should suggest diabetes mellitus. 



