174 COMPOSITION OF THE BODY 



from time to time and treat with iodine and with Fehling's solution. 

 The test should be made at 35° C. For control add some of the 

 boiled extract to another portion of the starch mixture. Boil- 

 ing destroys the enzyme, and this will show whether the changes 

 are due to its action or not. 



2. Invertase may be detected by its action in the extract when 

 added to a solution of cane-sugar. In such tests the reducing 

 power of the sugar should be tested first, as it is probable that 

 some reducing sugar will be extracted with the enzyme. After 

 the extract has acted upon the solution for an hour, the reducing 

 power of the mixture should be determined again and the in- 

 crease accredited to invertase. 



3. Cytase, a cellulose-dissolving ferment has been found in fun- 

 gal mycelia and in a number of monocotyledonous plants. Its ef- 

 fects can be tested upon cotton fiber acidulated with acetic acid. It 

 causes cellulose to swell and gelatinize. Only simple celluloses 

 are affected ; lignified, cutinized, or suberized walls resist its action.' 



4. Suspend some finely divided coagulated proteid in a few cc. 

 of the extract. Acidify with 0.025 per-cent. hydrochloric acid. 

 The disappearance of the proteid indicates the presence of trypsin. 



5 . Add to some of the extract an emulsion of the oil from the 

 same kind of seeds from which the extract was made. If lipase 

 is present it will be indicated by the increased acidity of the mixture 

 as indicated by the greater quantity of standard alkali solution 

 necessary to neutralize it after digestion. The increase in the 

 amount of free fatty acid will be due to the action of the lipase. 

 This increase may be demonstrated by adding neutral litmus solu- 

 tion at the beginning of the experiment. 1 



1 Directions for more detailed work on ferments may be obtained by consulting the 

 following works : 



Green, J. Reynolds. The Soluble Ferments and Fermentation. Cambridge. 

 1899. 



Green, J. Reynolds. Vegetable Physiology. London. 1900. 



Effront, J. Les Enzymes et leurs Applications. Paris. 1899. 



Osborne, T. B. On the chemical nature of diastase. Conn. Agric. Exp. Sta. 

 18th Ann. Rep. 192-207, 1894. 



