BOOK VIII 



THE FUNCTIONS OF THE KIDNEY 



THE URINE 



THE urine, continuously secreted by the kidneys, averages about 

 1,500 c.c. (50 ounces) in twenty -four hours. The larger part of this 

 amount is passed during the day, but in certain diseased conditions 

 more may be passed during the night. For this reason, some clinicians 

 have the urine passed during the twenty-four hours collected in two 

 portions. The day urine is taken, say, from 8.30 a.m. to 8.30 p.m., 

 the bladder being emptied at both these times. The remainder is the 

 ''' night urine." Children pass considerably less urine than an adult. 

 At five years the daily amount is about 390 c.c., at twelve years about 

 830 c.c., about fifteen the amount begins to approximate to that of 

 the adult. 



As the urine passed at different times during the day varies con- 

 siderably in composition, it is usual to take the total urine of twenty- 

 four hours for purposes of clinical analysis. Various factors modify 

 the amount passed. An increased secretion follows a large consump- 

 tion of food or drink, and exposure to cold. On the other hand, in- 

 gestion of little food or drink, exposure to heat, great muscular work, 

 the conditions which produce sweating, lead to a diminished secretion. 



Normal urine is a transparent, limpid, watery fluid, yellow in 

 colour. When shaken in a test-tube, there is a little froth, which 

 does not last long. When certain pathological bodies are present, 

 particularly bile and protein, the urine is less mobile, and the froth 

 much more marked. Thus, the presence of albumin may be indicated 

 by the froth on shaking. 



The odour of healthy urine is described as aromatic. After stand- 

 ing for some time, this changes to an " ammoniacal " smell, owing to 

 the action of organisms (Micrococcus urece) which fall into it, and 

 by their growth break down the urea present, with the liberation 

 of ammonia. 



The specific gravity of urine, as tested by the instrument known 

 as the urinometer, is on an average 1015 to 1025. These figures 

 apply to the twenty-four-hour sample; for samples casually taken 



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