368 USES OF THE LIVER DUCTLESS GLANDS 



imposed. The plates of cholesterin often show a cleavage at one corner, 

 the lines running parallel to the borders. Frequently the plates are' 

 rectangular and sometimes they are lozenge-shaped. 



The proportion of cholesterin in the bile usually is estimated at 0.62 

 to 2.66 parts per thousand. In a single examination of the human bile, 

 however, the proportion was 0.618 of a part per thousand (Flint). 



Bilirubin. The coloring matter of the bile, bilirubin (C 32 H 36 N 4 O 6 ), 

 bears a certain resemblance to the coloring matter of the blood and is 

 supposed to be formed from it in the liver. It gives to the bile its 

 peculiar tint and has the property of coloring the tissues with which it 

 comes in contact. Whenever the flow of bile is obstructed for any con- 

 siderable time, the coloring matter is absorbed by the blood and can 

 readily be detected in the serum and in the urine. It also colors the skin 

 and the conjunctiva. It is soluble in chloroform, by which it is dis- 

 tinguished from biliverdin, and forms soluble combinations with alkalies, 

 in which form it is thought to exist in the bile. It probably is formed 

 in the liver from the hemoglobin of the red blood-corpuscles. When 

 exposed to the air or to the influence of certain oxidizing agents, it 

 assumes a greenish color and is changed into biliverdin. It is unneces- 

 sary to follow the various other changes produced by spontaneous 

 decomposition or by the action of reagents. 



Tests for Bile. A simple test for bile-pigment is the following r 

 A ten per cent solution of iodin in alcohol is floated on the suspected 

 solution in a test tube. If the coloring matter of bile is present, a green 

 ring will appear between the two liquids. 



A delicate test for the biliary salts in a clear solution not containing 

 albumin is what is known as Pettenkofer's test : To the suspected liquid 

 are added a few drops of a strong solution of cane-sugar. Sulphuric 

 acid is then slowly added, to the extent of about two-thirds of the bulk 

 of the liquid. It is recommended to add the acid slowly so that the 

 temperature shall be but little raised. If a large quantity of the biliary 

 salts is present, a red color shows itself almost immediately at the bot- 

 tom of the test tube, and this soon extends through the entire liquid, 

 rapidly deepening until it becomes dark lake or purple. If the biliary 

 matter exists in small proportion, it may be several minutes before a 

 red color makes its appearance, and the change to a purple is corre- 

 spondingly slow, the whole process occupying fifteen to twenty minutes. 



EXCRETORY ACTION OF THE LIVER 



Although the liver produces a greater or less quantity of urea, this 

 substance is discharged from the body chiefly in the urine and mere 



