CHAPTER XXXVII 



THE URINE 



Quantity. A man of average weight and height passes from 1400 

 to 1600 c.c., or about 50 oz. daily. This contains about 50 grammes 

 (1J oz.) of solids. For analytical purposes it should be collected in 

 a tall glass vessel capable of holding 3000 c.c., which should have a 

 smooth-edged neck accurately covered by a ground-glass plate to 

 exclude dust and prevent evaporation. The vessel, moreover, should 

 be graduated so that the amount may be easily read off. From the 

 total quantity thus collected in the twenty-four hours, samples should 

 be drawn off for examination. 



Colour. This is some shade of yellow which varies considerably 

 in health with the concentration of the urine. It is due to a mixture 

 of pigments ; of these urobilin is the one of which we have the most 

 accurate knowledge. Urobilin has a reddish tint, and is undoubtedly 

 derived from the blood pigment, and, like bile pigment, is an iron- 

 free derivative of haemoglobin. The theory usually accepted con- 

 cerning its mode of origin is that bile pigment is in the intestines 

 converted into stercobilin; that most of the stercobilin leaves the 

 body with the faeces ; that some is reabsorbed and is excreted with 

 the urine as urobilin. Both stercobilin and urobilin are very like 

 the artificial reduction product of bilirubin called hydrobilirubin (see 

 p. 511). Normal urine, however, contains very little urobilin. The 

 actual body present is a chromogen or mother substance called 

 urobilinogen, which by oxidation for instance, standing exposed to 

 the air is converted into the pigment proper. In certain diseased 

 conditions the amount of urobilin is considerably increased. 



The most abundant urinary pigment is a yellow one, named 

 urochrome. It shows no absorption bands. It is probably an oxida- 

 tion product of urobilin. (Riva, A. E. Garrod.) 



Reaction. The reaction of normal urine is acid. This is not due 

 to free acid, as the uric and hippuric acids in the urine are combined 

 as urates and hippurates respectively. The acidity is due to acid 

 salts, of which acid sodium phosphate is the most important. Under 



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