512 MANUAL OF HISTOLOGY. 



intermediate step, and then into grape sugar. Its amount in the living 

 cell is so small that we are unable actually to prove its presence there, but 

 immediately after death it increases considerably in quantity. Besides 

 this, fatty matters are encountered in the glandular elements, and frequently 

 also biliary pigment in the form of granules. The hepatic cell, however, 

 fabricates besides several other substances of great importance in the 

 formation of bile, as we shall see presently in considering this secretion. 

 It is not improbable that the formation of glycogen, and certain of the 

 constituents of bile, are only different portions of one and the same 

 mutative chemical process. 



The fatty matters of hepatic tissue still await accurate analysis. 



268. 



The l/ile, an exceedingly decomposable secretion, is, as it flows 

 immediately from the liver, a clear and rather thin fluid of alkaline 

 reaction. Its colour is sometimes reddish yellow, as in the carnivora, 

 and sometimes greenish, as in the case of the vegetable feeders. What- 

 ever its tint be at the outset, it always turns to green on exposure to 

 the air. To the taste it is sweetish bitter, leaving little aftertaste. 

 During its sojourn in the gall-bladder its characters become changed, its 

 alkalinity appears more marked, it receives an admixture of mucus, the 

 colour deepens to brown, and it becomes more concentrated. The sp. gr. 

 of human bile is usually accepted as 1 '026-1 '032. 



The fluid is usually completely homogeneous, without either granules 

 or fat globules ; nor do hepatic cells make their appearance in it } owing 

 to the small calibre of the biliary capillaries. 



The most important and essential constituents of bile are the com- 

 pounds of sodium with two peculiar acids, and the pigmentary substances. 



These two acids, taurocholic and glycocholic, have been already 

 considered ( 27). From the fact that they are absent from the blood, 

 we are forced to the conclusion that they are generated in the liver. 

 Their mode of origin, however, is still a matter of great obscurity. 



For a long time the greatest uncertainty prevailed as to the nature of 

 the colouring matters of the bile. It was not until after Staedeler's 

 beautiful investigations were published that any progress was made in 

 this direction (p. 53). Fresh bile appears to 

 contain only two of those pigmentary matters 

 discovered by this chemist, namely, the more 

 essential bilirubin and biliverdin. 



Bilirubin (fig. 506) may be obtained from 



t/MF /Sk ^ ^ slightly acidulated bile by agitation with chloro- 

 MK Ml Rl & form. That it is nearly allied to hsematin, and 

 lias its origin in the destruction of the pigment of 

 the blood-cells in the parenchyma of the liver, 

 can hardly be doubted, although we were 

 obliged at p. 50 to negative the question of 

 identity of the two substances. The peculiar 

 crystalline form of this pigment is also against 



Tig. 506.-crystais of bilirubin our *f epting .** as identical with heematin, its 

 obtained from its solution in crystals assuming a whetstone figure. 



Very small crystalline bodies, made up of 



bilirubin in irregular and sometimes stalk-like masses, may be met with 

 in the bodies of the hepatic cells at times. 



