64 EXPERIMENTAL PHYSIOLOGY 



a test tube with this solution. Let it stand a moment. 

 Do the oil drops reunite after separation as when shaken 

 with water? Is the oil dissolved? (This is an emulsion, 

 which is formed when separated particles of oil are kept 

 from reuniting by some surrounding medium. Such action 

 is called mechanical as contrasted with the chemical action 

 of a ferment.) 



Boil some olive oil with caustic soda. Smell this solu- 

 tion and describe its odor. Taste it. What has been 

 formed? Is this product soluble in water? (The conver- 

 sion of fat into soluble soap is called saponification. This 

 action is performed by the pancreatin, without boihng, by 

 aid of the contained ferment called steapsin.) 



D. Action of Bile. Examine some of the gall from an ox 

 gall. What is its color? taste? (Human gall, or bile, is 

 golden brown.) Test some of this ox gall with litmus. Is 

 it acid or alkaline? Shake up some of the gall with olive 

 oil. Does it emulsify the oil? Add some of the gall (bile) 

 to minced white of egg and keep at 36° C. for twenty-four 

 hours. At the end of that time test the mixture with food 

 tests. Has the bile converted the white of egg? Repeat, 

 using starch paste instead of white of egg, and follow with 

 food tests. Has the bile converted the starch? (Bile con- 

 tains no enzyme and hence can not convert any form of 

 nutrient.) 



XXXIX. — Digestion of Mineral Salts (Optional). 



Apparatus, — Phosphate of lime, sodium chloride (common salt)^ 

 dilute hydrochloric acid (10%), test tubes, evaporating dish. 



Directions. — Shake up some sodium chloride with water 

 in a test tube. Do the same with some phosphate of Ume 



