2Q2 PHYSIOLOGICAL CHEMISTRY. 



the decomposition of lecithin, and phosphocarnic acid. It is claimed 

 that on the average about 2.5 per cent of the total phosphorus elimi- 

 nation is in organic combination. 



PIGMENTS. 



There are at least three pigments normally present in human 

 urine. These pigments are urochrome, urobilin and uroerythrin. 



A. UROCHROME. 



This is the principal pigment of normal urine and imparts the 

 characteristic yellow color to that fluid. It is apparently closely 

 related to its associated pigment urobilin since the latter may be 

 readily converted into urochrome through evaporation of its aque- 

 ous-ether solution. Urochrome may be obtained in the form of a 

 brown, amorphous powder which is readily soluble in water and 

 95 per cent alcohol. It is less soluble in absolute alcohol, acetone, 

 amyl alcohol and acetic ether and insoluble in benzene, chloroform 

 and ether. Urochrome is said to be a nitrogenous body (4.2 per 

 cent nitrogen), free from iron. 



B. UROBILIN. 



Urobilin, which was at one time considered to be the principal 

 pigment of urine, in reality contributes little toward the pigmenta- 

 tion of this fluid. It is claimed that no urobilin is present in 

 freshly voided normal urine but that its precursor, a chromogen 

 called urobilinogen, is present and gives rise to urobilin. upon de- 

 composition through the influence of light. It is claimed by some 

 investigators that there are various forms of urobilin, e. g., normal, 

 febrile, physiological and pathological. Urobilin is said to be very 

 similar to, if not absolutely identical with, hydrobilirubin (see 

 page 173). 



Urobilin may be obtained as an amorphous powder which varies 

 in color from brown to reddish-brown, red and reddish-yellow de- 

 pending upon the way in which it is prepared. It is easily soluble in 

 ethyl alcohol, amyl alcohol and chloroform, and slightly soluble in 

 ether, acetic ether and in water. Its solutions show characteristic 

 absorption-bands (see Absorption Spectra, Plate II). Under 

 normal conditions urobilin is derived from the bile pigments in the 

 intestine. 



Urobilin is increased in most acute infectious diseases such as ery- 

 sipelas, malaria, pneumonia and scarlet fever. It is also increased 



