446 BILE. [BOOK n. 



bright green, or a dirty green, according to circumstances, being 

 much modified by retention in the gall-bladder. The reaction 

 is neutral or alkaline. The following may be taken as the average 

 composition of human bile taken from the gall-bladder, and there- 

 fore containing much more mucus as well as, relatively to the 

 solids, more water than bile from the hepatic duct. 



In 1000 parts. 



Water 859'2 



Solids : 



Bile Salts 91'4 



Fats, &c. 9'2 



Cholesterin 2'6 



Mucus and Pigment ... ... ... 29'8 



Inorganic Salts ... ... ... ... 7*8 



" 140-8 



The entire absence of proteids is a marked feature of bile : 

 pancreatic juice, as we shall see, contains a considerable quantity, 

 saliva, as we have seen, a small quantity, normal gastric juice 

 probably still less, and bile none at all. Even the bile which has 

 been retained some time in the gall-bladder, though rich in mucus, 

 contains no proteids. The mucin of bile differs from that of saliva 

 ( 197) in being soluble in an excess of acetic acid, in not giving 

 rise to any reducing substance, and in containing a considerable 

 quantity of phosphorus; it resembles in some points nucleo- 

 albumin. 



The constituents which form, apart from the mucus, the great 

 bulk of the solids of bile and which deserve chief attention, are the 

 pigments and the bile-salts ; of these we shall speak immediately. 



With regard to the inorganic salts actually present as such sodium 

 salts are conspicuous, sodium chloride amounting to '2 or more per 

 cent., sodium phosphate to nearly as much, the. rest being earthy 

 phosphates and other matters in small quantity. The presence of 

 iron, to the extent of about '006 p. c., is interesting, since, as we 

 shall see, there are reasons for thinking that the pigment of bile, 

 itself free from iron, is derived from iron-holding haemoglobin : 

 some, at least, of the iron set free during the conversion of haemo- 



flobin into bile pigment, which probably takes place in the liver, 

 nds its way into the bile. Bile also appears to contain a small 

 quantity, at all events occasionally, of other metals, such as man- 

 ganese and copper; metals introduced into the body are apt to 

 be retained in the liver and eventually leave it by the bile. 



The small quantity of fat present consists in part of the complex 

 body lecithin. 



The peculiar body cholesterin, which though fatty looking (hence 

 the name ' bile fat') is really an alcohol with the composition C^H^O, 

 is conspicuous by its quantity and constancy. It forms the greater 

 part of most gall-stones, though some are composed chiefly of 



