OH. xxxvn.] THE URINE. 547 



sympathetic chain, from here to the inferior mesenteric gang- 

 lion, and ultimately reach the bladder by the hypogastric nerves. 

 Stimulation of these nerves causes contraction of the circular 

 fibres of the bladder, including the sphincter; (2) from the 

 second and third sacral nerves ; these run to the bladder by the 

 nervi erigentes. Stimulation of these nerves causes relaxation 

 of the sphincter and contraction of the detrusor urinse. (Zeissl.) 

 Langley and Anderson find however that stimulation of both sets 

 of nerves causes contraction of both longitudinally and circularly 

 arranged muscle bundles. 



CHAPTER XXXVII. 



THE URINE. 



Quantity. A man of average weight and height passes from 

 1,400 to i, 600 c.c., or about 50 oz. daily. This contains about 

 50 grammes (ii oz.) of solids. For analytical purposes it should 

 be collected in a tall glass vessel capable of holding 3,000 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 consider- 

 ably 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 concerning 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 pro- 

 duct of bilirubin called hydrobilirubin (see p. 504). 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 



y y 2 



