210 



THE BILE. 



of bile, since it has three additional absorption bands less distinct than 

 at C, but sufficiently well marked and differently situated from those of 

 bile. One of these additional bands is placed at about three-quarters 

 the distance from C to D, another a little to the left of E, and a third, 



Fig. 70. 



SPECTRUM OP CHLOROPHYLLS iff ALCOHOLIC SOLUTION. 



wider than the others, but very faint and ill-defined, about midway 

 between E and F. In the spectrum of chloroplrylle, also, notwithstand- 

 ing the strong absorption of light at the situation of the principal 

 bands, the yellow of the spectrum appears in its proper place and with 

 nearly its natural hue. An additional distinction of chlorophylle, as 

 compared with that of bile, is that its light does not terminate abruptly, 

 , but fades more or less gradually toward the refrangible end. 



The bile exhibits a peculiar reaction when treated with nitric acid, 

 owing to the effect upon its coloring matter. If a moderate quantity 

 of dilute nitric acid be added to fresh bile and the mixture shaken up, 

 the whole becomes of a bright grass-green, the first color produced by 

 oxidation of the bilirubine and biliverdine. But if the bile be brought 

 in contact, in a cylindrical glass vessel, with a layer of strong nitric 

 acid, especially if it contain a trace of nitrous acid, and allowed to 

 remain without agitation, a series of colored rings are produced at the 

 surface of contact of the two liquids, following each other in a definite 

 order, from the bile to the nitric acid, as green, blue, violet, red, and 

 yellow. These colors represent successive stages of oxidation and 

 , final destruction of the biliary coloring matter. The test is known as 

 s " Gmelin's bile test," and may be applied to other animal fluids in which 

 bilirubine or its derivatives are supposed to be present. 



Composition of the Bile. In its immediate composition the bile is 

 especially destinguished by the presence of the two peculiar biliary salts, 

 namely, sodium glycocholate and sodium taurocholate, which have been 

 described in Chapter VI., under their appropriate heads. It is evidently 

 these substances which give to the secretion its most important charac- 

 ters. They vary in relative quantity in the bile of different animals, 

 and perhaps also in that of the same species at different times. They 

 are produced, like the coloring matters, in the substance of the liver 

 itself, while other ingredients of the secretion, such as the various inin- 



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