186 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



substance of the starch-grains, may be unequally affected by ferments from the outside 

 toward the inside, and that therefore they must differ in their density. Special emphasis, 

 he believes, should be laid on the fact that the contours of these canals are sharply out- 

 lined, and that they usually remain narrow, while in the meantime the concentric layers 

 successively disappear. This may be clearly seen, especially in the seeds of wheat, where 

 different parts of the grain remain unchanged while others are already transformed into 

 a cellulose skeleton. In the ferment-resisting grains of potato and rice starch, after the 

 action for 24 hours of a strong ferment, single eroded grains can nearly always be found, 

 the number increasing after a few days; but the majority of the grains remain unaffected 

 in spite of repeated renewal of the ferment. This is most strikingly exhibited in the scarlet 

 bean and horse-chestnut, where a few single grains were found to be entirely intact at a 

 time when all the others were on the point of disappearing. 



It is an interesting fact, writes Baranetzky, that the structure of the grain varies 

 in single seeds of the same species of plants, as is undoubtedly proved by the differences 

 of the grains in their processes of erosion. It would seem, however, that during germi- 

 nation the majority of starch-gi'ains in one and the same seed are affected alike, but 

 differently in different seeds. It seems of little moment, he found, whether the entire sub- 

 stance of the starch-grain is permeated by the ferment, or whether the ferment action is 

 merely a superficial one. It is more than likely that the process of solution depends on 

 the concentration of the ferment solution. A highly concentrated ferment, he belie\^es, 

 will act so energetically that the outer layers of the grain are affected before the inner 

 parts have been permeated by ferment; the character of the colloidal ferment must neces- 

 sarily retard the latter procedure. On the other hand, if the mother-liquor surrounding 

 the starch-grain contains, as is usual, only a small amount of ferment in the living cell, 

 then the ferment gradually permeates the entire mass of the starch-grain and the central 

 soft portion is the first to come under the influence of the dissolving agent. The unequal 

 power of resisting ferments exhibited by different starch-grains can not, he believes, be 

 attributed to their cellulose content, for Phaseolus grains are an example of grains which 

 dissolve easily and leave a skeleton of cellulose behind after the granulose has been dis- 

 solved out of them. On the other hand, the more resisting grains of /Esculus hippocastanum 

 appear to contain much less celhdose. Baranetzky concludes that the differences in the 

 behavior of different grains toward ferments must be due to specific differences in the struc- 

 ture of the starch-grains of different plants. 



Important in tliis connection is an investigation of Wortmann (Zeit. f. physiolog. 

 Chemie, 1882, vi, 287) on the actions of bacteria on raw starch. His conclusions are as 

 follows : Bacteria possess the power of producing the same changes as diastase in starch- 

 grains, starch-paste, and soluble starch; they dissolve different starches with varying 

 rapi(hty; they will attack starches only in the absence of other carbohydrate nutrients, 

 and only when not deprived of air; the action of bacteria on starches is due to a ferment 

 secreted by them for this purpose, which, like diastase, can be precipitated with alcohol 

 and is soluble in water; the action of this ferment is purely diastatic; the ferment in itself 

 is capable of exerting its influence in the absence of acids ; bacteria also secrete the ferments 

 which are active in neutral starch-solutions; they act more energetically in weak acid 

 solutions; the manifestations of erosion agree exactly with those described by Baranetzsky, 

 as being caused by diastase. Wortmann's basic experiments were made with wheat starch 

 ill a preparation consisting of 1 or 2 drops of liciuid from putrefying beans or potatoes (in 

 which the Bacterium termo is abundant) in a 1 per cent solution of equal parts of sodium 

 chloride, magnesium sulphate, potassium nitrate, and acid ammonium phosphate. Erosion 

 begins at room temijerature in 5 to 7 days. 



Another, and perhaps the most important, investigation on the phenomena of erosion 

 of the starch-grain was made by Krabbe (Jalir. f. wissensch. Botanik, 1890, xxi, 520), in 



