3l8 FINE-STRUCTURE OF PROTOPLASMIC DERIVATIVES III 



swelling), for in this direction there are chiefly secondary and not 

 primary valencies that have to be overcome. 



A question which it is difficult to answer is why the hydrolysis 

 should occur with such characteristic rhythm in the case of these 

 microscopically homogeneous structures. If the microscopic segments 

 which are formed correspond to the chain lengths of the macro- 

 molecules, as Staudinger, Staudinger, and Sauter (1937) assume 

 that they do in the laminate break-down of synthetically produced 

 polyoxymethylene crystals, a mechanical cleavage perpendicularly 

 to the crystal axis should occur; but starch molecules are not of 

 microscopic length. Therefore, any such interpretation would not 

 apply to starch grains. Another possible explanation is that maybe the 

 submicroscopic capillary system of the object in question, corre- 

 sponding to the hydrolysis pattern, is periodically fine and coarse. 

 Without any such auxiHary hypotheses, however, it is possible to 

 suppose that in the hydrolytic break-down of fibrous or spherite 

 structures, fragments of uniform size are produced, just as, in the 

 mechanical pulverization of crystals or glass, only segments or 

 splinters of approximately the same size split off, this size having 

 nothing to do with the structural elementary units, but depending 

 solely upon the method of comminution applied. Macroscopically as 

 well, objects of entirely uniform structure can be split into pieces of 

 similar size which have not been pre-formed; thus, when ice is broken 

 up, a perfectly homogeneous slab of ice may split up into floes of 

 equal proportions, the size of which is by no means predetermined. 

 Under certain circumstances and, of course, to an enormously en- 

 larged scale, the pattern of the floes may be strikingly reminiscent of 

 the block structure represented in Fig. 157. In the opinion of Baden- 

 HUiZEN (1938) the "blocks" certainly are not pre-formed in the 

 structure of the starch grains. 



The submicroscopic structure of starch grains. Katz and Derksen (1933) 

 have established that different kinds of starch do not produce the 

 same X-ray spectrum. For example, the gramineous starch of wheat, 

 rice, corn and oats produces what is known as an A spectrum, 

 whereas potato starch has a B spectrum, and both, when formed into 

 a paste, produce a third, called the V spectrum. Starches with a B 

 spectrum have been converted at higher temperatures to the A kind 

 (Katz and Derksen, 1933); it has also been shown that the V spec- 



