PHENOMENA OF DIGESTIBILITY RAW STARCHES. 181 



Several observers have studied the phenomena of erosion of the starch-grains m sihi, 

 and a number have made comparisons of the changes which occur in situ and in vitro, 

 and there are also records of comparisons of the differences in the erosion phenomena 

 exhibited by the grains of different plants. Baranetzky (Die stiirkeumbildenen Fermente 

 in den Pflanzen, Leipzig, 1878) studied the starches of Polygonum fagopyrum, Phaseolus 

 multiflorus, MirahiUs julapa, Quercus pedunculata, /Esculus hippocastanum, Solanum 

 tuberosum, Fagopyrum esculenlum, Triticum sativum var. vulgare, and Oryza saliva. He 

 records that these starclies differed in their susceptibility to tlie action of ferments. Tiie 

 grains of buckwheat were the most easily affected; wheat and bean coming next; those of 

 potato, and especially rice, being the least easily affected. None was found to entirely resist 

 the influence of ferments. A given kind of starch was noted to be affected not only by 

 the ferments of the same plants but also by any kind of a starch-reducing ferment, all 

 kinds affecting it similarly. 



The experiments by Baranetzky include the actions of ferments of barley-malt, of 

 germinated seeds of Polygonum fagopyrum, MirahiUs jalapa, Phaseolus multiflorus (coty- 

 ledons), Esculus hippocastanum (cotyledons); of sprouting tubers of Solanum tuberosum 

 and Beta vulgaris; of stems and leaves of Phaseolus multiflorus; and of leaves of Eriobo- 

 trya japonica, Acanthus cordifolia, and Tradescantia discolor. The solution of the starch- 

 grains by the action of ferments was found to run parallel with the formation of starch- 

 paste. Since various starches differ in their resistance to the action of ferments, weak 

 ferments are limited in their action to grains that are easily affected, while energetic 

 ferments are required to influence such ferment-resisting grains as those of Solanum and 

 Oryza. The phenomena of the solution of the starch-grains are stated to refer only to 

 the actions of ferments, and not to any other influence. Bacteria, he notes, will naturally 

 form in a solution that has been allowed to stand, yet in the easily affected grains signs 

 of erosion appear in about 24 hours, at the time when, as he states, the fluid is still free 

 from organisms. Nor can the solution of the grains be due to the action of acids, because 

 grains of potato starch subjected to the macerating action of weak hydrochloric or acetic 

 acid for 33 days were entirely unchanged. Although the grains of horse-chestnut were 

 rendered transparent in a month after treatment with very weak acetic acid, this change 

 only slightly resembled that produced by the action of ferments. Baranetzky writes 

 that up to that time the changes which the starch-grains undergo by the action of ferments 

 ha\'e been observed only in the living plant, and that experimenters had not been able 

 to produce them artificially. 



Phaseolus Multiflorus. 



Baranetzky records that the dissolution in vitro of the starch-grains of Phaseolus 

 multiflorus always proceeds from the inside toward the periphery. After the ferment 

 has been allowed to act for 24 hours, it will be observed that some grains have a sort of 

 furrow, having the same shape as the grain, and which at first appears to be fifled with a 

 granular mass. This furrow widens and becomes entirely transparent, and its walls (lamellse) 

 break at several places, forming an outlet. It now becomes evident that this apparent 

 furrow is composed of a uniform, very transparent substance which remains in the place 

 of the dissolved starch-grains. The unchanged, dense mass of the grain gi'adually grows 

 less until finally only tiny flakes and streaks are left, which are irregularly distributed 

 on the periphery of the remaining skeleton. This skeleton is a clear, transparent disk, with 

 a delicate but distinct contour, and completely retains the form and size of the unclianged 

 grain, and the lamelhc are frecjuently even more marked than in the intact grain. 



In treating starch-grains in this state with iodine, Baranetzsky found that all the 

 denser parts give the usual iodine reaction, while the transparent parts remain colorless, 

 even after the prolonged action of the reagent; that the skeletons therefore no longer con- 



