326 



CHEMISTRY OF THE DIGESTIVE PROCESSES. 



oil of almonds, 5 parts of gum-arabic, and 35 parts of water. A solution 

 of litmus is prepared of such concentration and reaction that it shows a violet 

 colour when placed in test tubes about a centimetre in diameter in front 

 of white paper; in each test tube 10 c.c. of this dilute litmus solution are 

 placed to each five drops of emulsion are added ; then equal volumes of each 

 of the pancreatic extracts to be compared. From the times in which an equal 

 amount of red develops in the litmus in each case, the richness of the extracts 

 in fat- splitting ferment may be determined. Or a series of determinations 

 for each extract, using a varying quantity of it, may be made, and the 

 members of each series compared. 



The condition of the material to be digested has also a profound 

 effect upon the rapidity. The factors of most moment are 



1. Whether the material is fluid or solid. 



2. Whether it has previously been heated (cooked) or not. In the 

 case of starch, previous heating and formation of a starch paste shortens 

 the process in the ratio of hours to minutes ; in the case of proteids, 

 previous heat coagulation slows the after process of digestion. 



3. Materials which must first be dissolved, and must therefore be 

 attacked from the outside, are digested more quickly when in a finely 

 subdivided condition. 



Classification of Enzymes. 



