FERMENTATION OF CELLULOSE 163 



of the grain of malt rendered quite friable, and that for this 

 reason it is almost impossible to obtain a section of such a 

 grain. This is due to a cellulose-dissolving enzyme known 

 as cytase being secreted by the growing embryo, and the action 

 of this secretion must precede the action of amylase, if the 

 latter is to obtain access to the starch grains confined within 

 the cells of the endosperm. This can be demonstrated by 

 careful microscopic observation of the germinating barley 

 grain, but more simply by the following experiment, which 

 depends on the fact that cytase is destroyed at a temperature 

 above 60 C. 



A solution of malt extract is taken and divided into two 

 portions, say of 50 c.c. each. One of these is heated for half 

 an hour at 70 C. In each of the solutions a thin slice 

 of potato is suspended by means of a thin copper wire 

 attached to a glass rod or match stalk placed across the 

 top of the small beaker used for the experiment. A little 

 thymol is added to each of the solutions to prevent the 

 development of moulds or bacteria, and the two beakers 

 placed in an incubator at 40 C. for some days. It will 

 soon be noticed that the slice of potato in the solution 

 in which the cytase has not been destroyed becomes soft 

 and pulpy, the other slice remains quite hard, and the cell 

 walls can be seen by microscopical observation to be quite 

 unattacked. 



A similar result can be obtained if an infusion of raw oats 

 is used, and careful investigation by Horace T. Brown has 

 shown that the power of grain-feeding animals to digest such 

 food depends on the enzyme contained in the food, and not 

 on any cellulose-dissolving power possessed by the secretion 

 of the stomach of the animal. 



2. The decomposition of cellulose by bacteria in absence 

 of air can be demonstrated as follows : 



Some strips of filter paper are placed in a small flask and 

 a few c.c. of deposit from an ordinary sewage septic tank, or 



M2 



