The Digestion of Food 119 



into the intestines. As the food is pushed along over the 

 common opening of the bile and pancreatic ducts, a great 

 quantity of bile from the reservoir, the gall bladder, is 

 poured into the intestines. These two digestive fluids are 

 now mixed with the chyme and act upon it in the remark- 

 able manner just described. 



Experiment 49. To show the action of pancreatic juice on oils 

 or fats. Put two grains of pancreatin into a test tube. Add half a 

 teaspoonful of warm water, and shake well for a few minutes ; then 

 add a tablespoonful of sweet oil ; shake vigorously. 



A creamy, opaque mixture of the oil and water, called an emul- 

 sion, will result. This will gradually separate upon standing, the 

 pancreatic extract settling in the water at the bottom. When shaken 

 it will again form an emulsion. 



Experiment 50. To show the action of pancreatic juice on starch. 

 Put two tablespoonfuls of smooth starch paste into a goblet, and 

 while still so warm as just to be borne by the mouth, stir into it two 

 grains of the extract of pancreas. The starch paste will rapidly 

 become thinner, and gradually change into soluble starch, in a per- 

 fectly fluid solution. Within a few minutes some of the starch is con- 

 verted through intermediary stages into maltose and then into glucose. 

 Use the Fehling test for sugar. 



Experiment 51. To show the action of pancreatic juice on the 

 albuminous ingredients (casein) of milk. Into a half-pint bottle (an 

 infant's nursing bottle will answer and is easily obtained) put two 

 tablespoonfuls of cold water; add one grain of pancreatin, and as 

 much baking soda as can be taken up on the point of a penknife. 

 Shake well, and add four tablespoonfuls of cold, fresh milk. Shake 

 again. Now set the bottle into a basin of hot water (as hot as one can 

 bear the hand in), and let it stand for about forty-five minutes. 



While the milk is digesting, take a small quantity of milk in a 

 goblet, and stir in ten drops or more of vinegar. A thick, curd of 

 casein will be seen. 



Upon applying the same test to the digested milk, no curd will be 

 made. This is because the pancreatic ferment (trypsin) has digested 

 the casein into " peptone," which does not curdle. 



