156 BILE. 



seconds the stain appears violet by transmitted light. 

 The paper may be placed between two glass slips and 

 examined spectroscopically. Two faint bands to the 

 blue side of D ; one close to D, the other near the blue. 

 c. Surface tension test (Hay). Sprinkle a little flowers of 

 sulphur on the surface of the fluid, it will sink. Make 

 a control test with water and compare its behaviour 

 with water to which a little bile has been added. 



4. Pigments. Bili-rubin and bili-verdin are changed by oxida- 



tion. 



Gmelin's reaction. On mixing the fluid with HNO 3 con- 

 taining nitrous acid let two pools of the fluids flow 

 together on a plate a play of colours occurs passing 

 through green, blue, violet, red to fawn. 



If the reaction be performed in a tube the colours- 

 will be produced in successive layers above each other. 



5. Cholesterin: Obtained from gall stones. Dissolve a small 



pinch of powdered gall stone in 3 cm of equal parts 

 ether and alcohol, pass through a dry filter. Place 2 

 drops on a glass slide, cover, and let it evaporate slowly. 

 Irregular cholesterin crystals will separate out. When 

 regularly formed the crystals are rhombic plates with a, 

 corner broken out. 



When dry flow under the cover a mixture of H 2 SO 4 

 with a quarter volume of water, then a small quantity 

 of iodide of potassium solution. (Salkowski's Practicum.) 

 The cholesterin crystals colour brown, violet, or even 

 blue, and are partially dissolved. 



