THE DIGESTIVE APPARATUS AND NUTRITION 253 



ture of about 37 C. The milk curdles in a few minutes. In the 

 previous experiment the milk was curdled by the renuin ferment in 

 the artificial gastric juice. 



117. Action of Pancreatic Juice on Starch. Repeat Ex. 113, using, 

 instead of saliva, artificial pancreatic juice. 1 



118. Action of Pancreatic Juice on Proteids. Repeat Ex. 114, 

 osing artificial pancreatic juice instead of gastric juice, and carbonate 

 of soda solution instead of muriatic acid. 



119. The Emulsifying Effect of Pancreatic Juice. Rub together, 

 in a mortar, some olive oil, or cod-liver oil, with pieces of fresh pan- 

 creas. An emulsion results. Shake together in a test tube some 

 olive oil and a little artificial pancreatic juice, as used in preceding 

 experiments. An emulsion occurs as before. Boil some artificial 

 pancreatic juice to destroy the ferment. It still forms an emulsion 

 with oil. In the experiments on fats (Exs. 97-100) it was seen that 

 an alkali, or a soluble proteid, forms an emulsion with fats. Natural 

 pancreatic juice contains both alkali and proteids. Hence, even when 

 boiled, pancreatic juice emulsifies fats. 



120. Bile. Obtain bile at a slaughterhouse. Observe its color. 

 Test with litmus paper. It is neutral or alkaline if fresh. 



121. Action of Bile in Fats. Shake some olive oil in a test tube, 

 with five times its bulk of bile. Make a similar mixture of olive oil 

 and water, and observe in which case the emulsion lasts longer. 

 Shake up bile with olive oil, to which a little oleic a'cid is added. 

 The emulsion lasts longer than before. 



122. Action of Bile in Filtration and Absorption. Into each of two 

 small funnels of exactly the same size, put a filter paper. Moisten 

 one with water and the other with bile. Pour into both equal 

 amounts of almond oil, and after covering to prevent evaporation, set 

 aside twelve to fourteen hours. The oil passes through the filter 

 moistened with bile, but scarcely at all through the other. 



1 Add a little powdered pancreatine to a 1 per cent solution of car- 

 bonate of soda. Commercial pancreatine commonly contains both the 

 starch-digesting ferment, qmylopsin, and the proteid-digesting ferment, 

 trypsin. 



MACY'S pnvs. 16 



