XVII.] INTESTINE. BILE. PANCREATIC JUICE. 1S7 



7. Mount a few crystals of cholesterin' in water 

 and examine them under a microscope, they 

 consist of rhombic plates. 



S. Irrigate the crystals with strong sulphuric acid ; 

 they turn red. 



9. To a small quantity of chloroform in a test-tube 

 add a little cholesterin and shake, the cholesterin 

 •will dissolve; add strong sulphuric acid and 

 gently shake, the upper (chloroform) layer will 

 turn bright red. 



10. Digest a little fibrin in 10 c.c. of artificial gastric 

 juice ; when the fibrin is dissolved add drop by 

 drop, bile which has been decolourized by filtering 

 through animal charcoal; a precipitate will be 

 formed consisting of parapeptone, peptone and 

 bile acids. (If excess of bile is added especially if 

 it contains taurocholic acid, the peptone and bile 

 acids will be more or less completely dissolved.) 



11. Add to the preceding 5 c.c. of '4 p.c. HCl and a 

 few flocks of swollen fibrin; the fibrin will shrink 

 and will be digested slowly or not at all. Bile 

 acids prevent gastric juice from digesting proteids. 



1 Cholesterin may be prepared from gall etones (those which have 

 a soapy feel) in the following manner. Powder the gall stones and 

 add a small quantity of strong spirit (or absolute alcohol) and boil ; 

 filter hot, using a hot- water funnel ; on cooling, cholesterin ci-ystals 

 will separate out. Collect the crystals, place them in a small 

 quantity of spirit containing a little sodium hydrate and boil. On 

 cooling, purified cholesterin crystallizes out ; wash the crystals with 

 water. 



