APPARATUS FOE PHYSIOLOGICAL USE. 273 



also acts upon starch and converts it into sugar, even more 

 readily than the salivary ferment does. 



I have here in a test-tube a little fresh starch paste, and 

 to this I add some solution of caustic potash and a few 

 drops of a solution of copper sulphate. On boiling the 

 mixture no change takes place in the colour. But if I now 

 repeat this experiment with starch paste which has been 

 allowed to stand in the water-bath for a short time after 

 the addition of a few drops of glycerine extract of pan- 

 creas, the result is very different. The mixture instead of 

 remaining blue becomes yellow and very turbid, and 

 deposits an orange-yellow sediment. This is due to the 

 reduction of the copper sulphate to copper oxide by the 

 grape sugar, which has been formed from the starch paste 

 by the pancreatic juice. The starch paste itself has no 

 such action, and so the mixture containing it remains blue 

 after boiling. The third action of the pancreatic ferment 

 is upon oils and fats. It first of all forms with them an 

 emulsion. Here is some oil, and if I add to it a little of 

 this solution of pancreatine and shake it up, you will find 

 it will form a milky emulsion, more especially if you add 

 to it a little water. But this is not all, for it splits up the 

 fat into fatty acids and glycerine, and the fatty acids 

 uniting with some of the alkalis found in the intestines 

 form soaps, and the soaps, along with the fatty acids and 

 the unaltered particles of fat, pass readily through into the 

 circulation ; so that one of the chief uses of the pancreatic 

 ferment is to render fat capable of absorption. 



The only remaining ferment is that of the intestinal 

 juice, and this is neither so good for demonstration, nor 

 so easy of investigation as either of the other two. If 

 you look into the subject, you will find that the action of 

 the intestinal ferment is stated very differently by different 

 observers. The reason of this, in all probability, simply 

 is that its action is not so definite as that of the other 

 ferments, and not so readily exerted upon the unaltered 

 constituents of food, which we are accustomed to use in our 

 experiments, as upon the residues which are left by the 

 other ferments in the intestines. After the other ferments 

 have acted upon the constituents of the food the intestinal 

 ferment comes into action, and completes the work which 

 they have begun. 



VOL. II. T 



