78 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



The porosity possessed by starch-grains in common with spherocrystals of other car- 

 boli>'drates was especially studied. Meyer states that starch-grains are porous like the 

 spherocrystals of inulin and amylodextrin whose individual trichites are not recognizable, 

 and that they contract when water is withdrawn and expand upon the addition of water. 

 The pores are exceedingly small, and can scarcely be seen with the highest power of the 

 microscope. They absorb approximately as much glycerine as water, and also take up alco- 

 hol, certain dye solutions, etc. Corn and potato starch placed in a concentrated solution of 

 methyl violet is stained completely. If the stained grains, after being washed, are placed 

 in glj'cerine, they lose the stain, the coloration disappearing fii-st in the peripheral layers. 

 If the intensely stained grains are put into a dilute solution of calcium nitrate, it can be 

 seen that the methyl violet is deposited in the largest cjuantities in those layers which are 

 relatively porous and slightly refractive. In Berlin blue the less refractive layers also 

 stained the more deeply. 



As in other crystals of carbohydrates, Meyer observes that the trichites of the starch- 

 grain are arranged in a radial manner and placed at right angles to the main mass. In 

 spherical starch-grains the easiest separation was found to be in the direction of the radii, 

 and in eccentric-layered grains along the lines which join the center to the periphery, or 

 perpendicular to the layers. The radial trichite structure is rarely seen very distinctly 

 in starch-grains, but not infrequently such a structure could with definiteness be detected 

 in potato starch. The spherical, concentric-layered grains behave optically exactly as 

 the spherocrystals of amylodextrin, and as though they were composed of trichites arranged 

 radially, and whose small optic axis of elasticity runs lengthwise. 



Meyer contradicts the statement of Mikosch that isolated trichites are not doubly re- 

 fractive, and holds (to the contrary) that every undissoh'ed tricliite of a starch-grain, whether 

 it consists of amylodextrin or amylose, behaves just like the isolated trichites of amylodex- 

 trin crystals. When spherical starch-grains are allowed to soak slowly, the optical properties 

 of the trichites persist as long as the minutest trichitic radial structure of the swollen grain 

 can be seen. Starch-grains, he notes, are lamellated as are the spherocrystals of inulin and 

 amylodextrin, and the lamellse become visible because in equal volumes of different layers, 

 the \'olunies of the pores standing in \'arying relation to the volumes of the trichites. 



Meyer quotes Niigeli's statement that the lamellar lines in starch-grains are either the 

 boundaries between two substances unequally refractive, or the entire space is filled with a 

 substance of varying density — at times watery lamellae in a denser substance and at other 

 times denser lamellje in a watery substance. 



Meyer states that since starch-grains are composed of various kinds of a-amylose, 

 /3-amylose, and amylodextrin trichites, and even probably of a mixture of crystals of these 

 substances, it is evident that the various layers consist of varying mixtures of these trichites. 

 A direct proof that such a relation exists, he holds, lies in the fact that when sorghum 

 starch is colored with iodine, many layers become blue and others red because some lamelhe 

 contain more amylose and others more amylodextrin, etc. By swelling the blue-colored 

 sorghum starch, or by treating the grains with saliva, it can be further shown that in differ- 

 ent layers the number of a-amylose and /S-amylose trichites varies. 



Referring to comparisons of the starch spherocrystal with other spherocrystals, Meyer 

 notes that the multiplicity of form observed is in striking contrast with the uniformity 

 of shape of artificial spherocrystals, and that it must be remembered that the relations 

 under which artificial spherocrystals ordinarily grow are similar, while those under which 

 starch-grains grow are very varied. Starch-grains develop in chromatophores which are 

 in the form of viscous droplets, and whose substance completely surrounds the growing 

 grain. These viscous droplets produce the crystallization material, and every layer of each 

 droplet, however thin, may furnish crystallization substance. The amount of crystalline 

 matter formed, he states, is dependent upon the quantity of active mass of the cliromato- 



