CHAPTER XXXTX 



THE URINE 



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

 to 1600 e.c., or about 50 fluid oz. daily. This contains about 60 

 grammes (1J oz.) of solids. 



Colour. This is some shade of yellow which varies considerably 

 with the concentration of the urine. It is due to a mixture of pig- 

 ments ; of these the most abundant is a yellow one, originally 

 named urochrome by Thudichum, whose investigations have in the 

 main been confirmed and supplemented by the recent work of 

 Dombrowski. It shows no absorption bands, and does not fluoresce 

 with zinc -salts as urobilin does. It yields a pyrrol derivative 

 which is not haemopyrrol, and so urochrome is probably not related 

 to urobilin. It contains 11-1 per cent, of nitrogen and 5 per cent, 

 of sulphur, most of which is easily split off as sulphide by cold 

 alkali. It is probably derived from protein. 



Urobilin, which is normally present in small quantities only, 

 has a reddish tint, and like bile pigment is an iron-free substance. 

 It has an absorption band near the F line. The bile pigment in 

 the intestines is converted into stercobilin, most of which leaves the 

 body with the faeces ; some, however, is reabsorbed and is excreted 

 into the urine, and is then called urobilin (see p. 534). A chromogen 

 or mother-substance called urobilinogen, which by oxidation for 

 instance, standing exposed to the air is converted into the pigment 

 proper, is more abundant than urobilin itself. In certain diseased 

 conditions the amount of urobilin is considerably increased. 



Uroerythrin, the colouring matter of pink urate sediments, 

 appear to be a small but constant constituent of urine, but its 

 origin is unknown. Normal urine contains also a trace of hcemato- 

 porphyrin, and the amount is increased in certain diseased states. 



Reaction. The reaction of normal urine is acid ; this is not due 

 to free acid, but to acid salts, of which acid sodium phosphate is the 

 most important. The uric and hippuric acids of the urine are 

 combined as urates and hippurates respectively. Under certain 

 circumstances the urine becomes less acid and even alkaline; the 

 most important of these are as follows : 



582 



