STARCH-SUBSTANCE, AND THE STRUCTURE, ETC., OF THE STARCH-GRAIN. 19 



fouiul to constitute 2.96 per cent of the starch, while the remaining 97.04 per cent was 

 recorded as being made up of 60.45 parts of amidine and 39.55 parts of amidin soluble. 



Payen and Persoz (Ann. de chim. et phys., 1834, lvi, 337) regarded the starch-sub- 

 stance as a single body, wliich they refer to as amidone. 



Gu(5rin-Varry in his second article states that the amidone of Payen and Persoz is a 

 mixture of two substances, one soluble and the other insoluble in cold water; and in his 

 third article he studies the actions of diastase on starch, and the characteristics of starch- 

 paste and the sugar formed, and he refers to the great resistance of raw starch to the action 

 of malt extract. He placed a preparation of raw potato starch and malt extract in a sealed 

 tube, keeping it at a temperature of 20 to 26 C. for 63 days, and found upon microscopic 

 examination at the end of tliis period that the grains showed no alteration. In his fourth 

 article he fm'ther considers the three components of starch, as held by him (see also 

 Chapter III, pages 86 and 177). 



Fritzsche (Ann. d. Physik u. Chemie, 1834, xxii, 129) seems to have been the first 

 to study the form and structure, and the mechanism of formation of the starch-grain. 

 He, in the first place, takes exception to the assertion of Raspail that every grain is com- 

 posed of two substances, one an enveloping membrane or integument (Hiille) which is 

 insoluble in water, and another part wliich is intraintegumentary and soluble in water. 

 The author's studies were mostly made with potato starch, but confirmed by observations 

 on other starches. He states that the grains of potato starch have a variety of forms and 

 sizes, and that the normal shape is that of a somewhat compressed, oval structure. A 

 uni\-ersal and constant characteristic, he records, is the presence of concentric rings which 

 vary in distinctness, regularity, arrangement, and number. These rings proceed from a 

 spherical point which, on account of its peculiar chemical relation, he terms the kernel or 

 nucleus (Kern) of the gi'ain (in later years and at present known as the hilum) . The hilum 

 was not always found to be located at the center, but might be anywhere in the long axis 

 of the grain. From the transparency of the hilum he was led to believe that it is a funnel- 

 like hole, which he thought proved by the fact that when a grain is compressed between 

 glass plates the hilum retains its position and canals are never observed to run from this 

 point peripherally. About this spherical hilum rings are arranged, the inner ones usually 

 uniformly, and the outer ones spread out more on one side of the grain than the other, 

 producing an oval shape. Every grain he states is composed of as many concentric 

 layers as there are rings. 



Fritsche then considers the question as to whether the outermost layer is produced 

 first in the form of a skin (Haut), and then the inner part by infiltration; or whether the 

 hilum is the first part formed and the layers deposited on it. This he found most easily 

 answered by examining compound grains which are found among the simple grains, 

 and which he states may be regarded as deviations or monstrosities. Observations of 

 these grains led him to conclude that all grains are formed by the deposition of the outer 

 layers upon the mner. The compound grains he believes have arisen tlirough the union 

 of two grains in apposition by means of the deposition of a conmion combining layer, or 

 by a smaller grain being inclosed by a layer of a larger grain during the process of growth 

 of the latter, such grains always having a small, distinct space present between the fused 

 grains. The outermost layer of the starch-grain was found to have a special density, by 

 which it can resist external influences better than the inner layers and he gives this as the 

 reason why unbroken grains are insoluble in water, and why crushed grains are soluble. 

 The reason for the greater density of the outermost layer he attributes to its being in con- 

 tact for a long time with the cell-sap which contains a large amount of vegetable albumin; 

 or that the grains may be covered with a precipitate that could easily be formed from an 

 albuminous body. He believes that differences in the densities of the layers account for 

 their visibility, and that the variations in density are perhaps owing to the influence of 



