Experiment 74.  Filter A, and carefully neutralize the filtrate with very dilute hydrochloric or acetic acid, equal to a precipitate of alkali-albumen.  Filter off the precipitate, and on testing the filtrate, peptones are found.  The intermediate bodies, the albumoses, are not nearly so readily obtained from pancreatic as from gastric digests.

  Experiment 75.  Filter B and C, and carefully neutralize the
  filtrates.  They give no precipitate.  No peptones are found.

Experiment 76. To show the action of pancreatic juice upon the albuminous ingredients (casein) of milk.  Into a four-ounce bottle put two tablespoonfuls of cold water; add one grain of Fairchild’s extract of pancreas, 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.  This digested milk is therefore called “peptonized milk.”

Experiment 77. To show the action of bile.  Obtain from the butcher some ox bile.  Note its bitter taste, peculiar odor, and greenish color.  It is alkaline or neutral to litmus paper.  Pour it from one vessel to another, and note that strings of mucin (from the lining membrane of the gall bladder) connect one vessel with the other.  It is best to precipitate the mucin by acetic acid before making experiments; and to dilute the clear liquid with a little distilled water.

Experiment 78. Test for bile pigments.  Place a few drops of bile on a white porcelain slab.  With a glass rod place a drop or two of strong nitric acid containing nitrous acid near the drop of bile; bring the acid and bile into contact.  Notice the succession of colors, beginning with green and passing into blue, red, and yellow.

Experiment 79. To show the action of bile on fats.  Mix three teaspoonfuls of bile with one-half a teaspoonful of almond oil, to which some oleic acid is added.  Shake well, and keep the tube in a water-bath at about 100 degrees F. A very good emulsion is obtained.

Experiment 80. To show that bile favors filtration and the absorption of fats.  Place two small funnels of exactly the same size in a filter stand, and under each a beaker.  Into each funnel put a filter paper; moisten the one with water (A) and the other with bile (B).  Pour into each an equal volume of almond oil; cover with a slip of glass to prevent evaporation.  Set aside for twelve hours, and note that the oil passes through B, but scarcely any through A.  The oil filters much more readily through the one moistened with bile, than through the one moistened with water.

Experiments with the Fats.