SECRETION DIGESTION ABSORPTION. 



and o.i-per-cent sodium carbonate. Place the mixture in the warm 

 water-bath. What change occurs in the butter ? After a time can 

 you detect the odor of butyric acid ? If so, what is its significance ? 



7. Action of Bile. You will be supplied with ox-bile. What 

 is its reaction ? 



(a) Test for bile pigments as follows (Gmelin's reaction) : To 

 a little bile on white porcelain add a few drops of fuming yellow 

 nitric acid. Note the changes in color from green to blue, yellow, 

 and brown-yellow. The test may also be done by placing a drop 

 of bile on white filter paper and bringing a drop of the acid in 

 contact with it. Color rings will be formed at the junction of the 

 bile and the acid. 



(b) Pettenkojer's Test for Bile Acids. Mix some ox-bile in a test- 

 tube with a small amount of strong sulphuric acid. Test the tem- 

 perature of the mixture with a thermometer, adding the acid 

 slowly. The temperature should not be higher than 70 C. or lower 

 than 50 C. Now add a ic-per-cent solution of cane sugar, 

 slowly, drop by drop, stirring with a glass rod. A red coloration 

 indicates the presence of bile acids. This reaction is masked by 

 using an excess of sugar or too high a temperature, since the sugar 

 is decomposed and colors the mixture a dark brown. 



(c) Mix some fresh butter in a test-tube with a few cubic centi- 

 metres of ox-bile. Mix a portion of butter in another tube with 

 bile and pancreatic extract. Place in the warm water-bath and 

 note results. 



8. Absorption of Fat. Starve a cat for twenty-four hours and 

 kill. Open the abdomen and note the condition of the mesenteric 

 lymphatics, the lacteals. Open a loop of small intestine. Scrape off 

 some of the mucous membrane. Tease some of the scrapings, on a 

 slide, with glycerin, after previous immersion in osmic acid J per 

 cent for twenty-four hours. Remove the excess of glycerin with 

 filter paper, and, covering the preparation with a cover slip, ex- 

 amine under the microscope. If fat-droplets are present in the 

 epithelium, they will be stained black or dark brown by the osmic 

 acid. Note results. 



