THE SUSCEPTIBILITY OF DIFFERENT STARCHES TO DIGESTIVE FERMENTS. 
By W. E. Stone. 
The question of the nutritive value and digestibility of many kinds 
of foods narrows down practically to a discussion of the amount of starch 
which they contain, since in many instances starch is the principal nutri- 
tive substance present. A knowledge, therefore, of the percentage of 
starch which such foods contain is about all we have been accustomed to 
ask in estimating their comparative value. Examples of such food ma- 
terials are potatoes and rice, while the various cereal preparations are 
also characterized by their starch content, although this is not the only 
nutritive substance which they contain. 
It has apparently not occurred to any one, or if so, such conjecture 
has not found circulation, that possibly there might be an inherent 
character in different starches by reason of which certain ones might be 
more or less digestible or nutritious than others. In the case of sugars 
this thought has lately come prominently to the front, Fischer particularly 
expressing the belief that certain sugars were more readily assimilated 
than others. Certain classes of sugars are known not to be digested or 
assimilated by the human organism. Certain others are not fermentable, 
and others ferment only slowly and incompletely. A study of the action 
of animal secretions, such as blood serum and infusions made from va- 
rious glands, upon the more complex sugars, shows conclusively that dif- 
ferent sugars exhibit a greatly varying range of resistance to these agents. 
It would seem, therefore, quite reasonable to expect that the starches 
existing in so many physical modifications and derived from so many 
different sources might also present some phenomena of this sort. A very 
serious difficulty, however, in the way of obtaining experimental data to 
show this is that starch considered as a chemical compound is an exceed- 
ingly complex and unstable substance, which under the influence of not 
extreme conditions is easily changed into other and different substances. 
Few compounds have been studied more than starch, and yet we know 
actually very little about it as such. We know much of its derivative and 
decomposition products, but starch itself is insoluble in its unchanged 
state, and so defies any direct study of its molecular condition. 
It is well known that starch is readily dissolved and at the same time 
converted into sugar by a number of the so-called enzymes or unorganized 
