BY DR. LAUDER BRUNTON. 499 



between it and 6, which disappears on the addition of liquor 

 sodse, and is replaced by a narrower band, also between 6 and 

 F, but nearer 6, the filtrate at the same time assuming a yel- 

 lowish color. If the solution is only very slightly alkaline, 

 both bands may be seen at once. Ammonia produces similar 

 changes in the color of the fluid, but the second band is very 

 faint when it is employed. On acidulation, the alkaline liquid 

 regains its red color, and the first band re-appears. By treat- 

 ing it with chloroform, a solution is obtained in which the first 

 band is visible, but is somewhat nearer b. 



Urine, especially when high-colored, exhibits the band at F, 

 though not very distinctly; but it may be clearly seen by pre- 

 cipitating the urine with lead acetate, decomposing the precipi- 

 tate b}' an acid, and examining the filtrate spectroscopically. 

 The addition of sodium hydrate causes the other band faintly 

 to appear, and when treated with chloroform in the same way 

 as bile, the solution and the position of the band seen in the 

 chloroform solution is altered in a similar manner. 



A substance presenting a similar band is obtained by acting 

 on a solution of bilirubin in liquor potassae or liquor sodae with 

 sodium amalgam, for several days, with exclusion of air (Maly). 



** 140. Bile Acids. The bile acids are taurocholic and 

 glycocholie acids. In the bile of the pig another acid, hyocho- 

 lic acid, is present. In the bile they are combined with soda, 

 and their soda salts form the so-called crystallized bile. These 

 acids are conjugate acids, composed of cholic acid in combina- 

 tion with taurine and glycocine. The presence of cholic acid 

 or its compound is recognized by a reaction known as 

 ^ J^ettenkofer' '& Test. This test shows the. presence only of 

 bile acids,but not of bile pigments or other constituents of bile. 

 Dilute some ox-bile with water and filter it. Put a little in a 

 test-tube, with a small piece of sugar or a little strong syrup. 

 Then add concentrated sulphuric acid drop by drop, shaking 

 the tube after each addition ; the temperature of its contents 

 should be kept as near 70 C. as possible, either by wanning it 

 if necessaiy, or putting it in cold water if it gets too hot. 

 Cholic acid is first precipitated and then dissolved by the sul- 

 phuric acid, the solution assuming a cherry-red and then a 

 beautiful purple color, which becomes gradually darker when 

 the liquid is allowed to stand. The reaction is hindered by 

 the presence of much pigment, oxidizing substances, and albu- 

 minous bodies, or bodies readily decomposed by sulphuric acid. 

 It is therefore better to use a solution of crystallized bile, if it 

 is at hand, than diluted bile. This reaction cannot be relied 

 on alone as positive proof of the presence of bile acids, for 

 amylic alcohol and other organic substances give a similar col- 

 oration. To show this, put a solution of albumin, or rather of 

 syntonin ( 7), into a test-tube with a little syrup, and add 



