CHAPTER 11. 



THE STARCH-SUBSTANCE, AND THE STRUCTURE, FORM, AND MECHANISM OF 



FORMATION OF THE STARCH-GRAIN. 



The wide distribution of starch in plant-life, its great food-value to both plants and 

 animals, and its extensive field of usefulness in domestic life and in many of the arts, 

 sciences, and trades, have made this substance a subject of study for generations. In 

 1S36, Poggendorff, in re\'ievving the literature of starch, wrote: 



No substance has been more investigated and yet less known. It affords a striking proof of 

 the diffuse manner in which a subject may be treated if it fall into improper hands. After ten years 

 of investigation, in which the most various views have been set up on the nature of starch, during 

 which all its characteristics as a proximate vegetable substance have been discussed, we are little 

 or nothing in advance of the old jwint of view; and, although perhaps we may not be wholly with- 

 out some extension of our knowlctlge on secondary points, we are still entirely without fundamental 

 grounds in proof of our having arrived at the truth. 



Even as late as 1885 Brown and Heron wrote: 



There is i)robably no one sul)ject in the whole range of chemistry which has attracted more 

 workers during the last 60 years than the transformation which starch undergoes when submitted 

 to the action of diastase or dilute acids; and in no respect are the opinions of chemists, even at the 

 present time, more at variance. 



As recently as 1895, Mej^er, in his elaborate memoir on starch, states that our 

 knowledge of the chemical substances which compose the starch-grain and the products 

 of decomposition is very meager. 



Notwithstanding the accumulation of an exceedingly voluminous literature and the 

 many advances in our knowledge of the chemistry of starch since the time of Poggendorff, 

 there are doubtless not a few biochemists who will hold that the statement of this investi- 

 gator and critic is applicable in a very large measure to our information at the present day. 



The synthesis, proximate constituents, microscopical structiu-e, and molecular constitu- 

 tion of starch, and the exact processes and products of the disintegration of starch thi'ough 

 the actions of dilute acids, alkalis, heat, oxidizing agents, enzymes, etc., are but few of the 

 very many instances of important problems which remain partially or wholly unsolved. 

 However, there are sufficient data pertaining to the subject-matter of this chapter to show 

 that starch is produced only in certain plants and in certain parts of plants, it being sub- 

 stituted by some analogous substance or substances in non-starch-producing plants or 

 plant parts; that the starch-substance from different sources is not identical, but exists in 

 a number of forms ; that the starch-grain is produced by specific starch-forming structures 

 which are more or less markedly differentiated, not only in different plants but also in 

 cUfferent parts of the same plant ; that the forms and other structural characteristics of the 

 starch-grain differ in certain ways in specific relationship to the peculiarities of the starch- 

 producing structures and other specific intracellular conditions; that the starch-grains pro- 

 duced by any given part of the plant may be very variable in size, form, and other 

 structural features, yet as a whole exhibit a certain type; that the starch-grain is a sphero- 

 crystal, and therefore has properties which render it available for study by certain crystallo- 



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