422 BILE. [BOOK n. 



green, or a bright green, or a dirty green, according to circum- 

 stances, 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 therefore 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 



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

 bulk of the solids of bile ami \vhich 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- 

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

 finds 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 cJiolesterin, 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 

 pigment. Insoluble in water and cold alcohol, though soluble 

 in hot alcohol and readily soluble in ether, chloroform &c., it is 

 dissolved by the bile-salts in aqueous solution and hence is present 

 in solution in bile. Its physiological functions are obscure. 



