14 DIFFERENTIATION AND SPECIFICITY OF STARCHES. 



spondinfily different stereoisomers, which is entirely consistent with the facts embodied 

 in tlie Uterature of adsorption-affinities — or whate^■er term one may use to express the 

 very conspicuous and important residual-affinities that exist in substances in which, 

 according to the laws of stoichiometry, the affinities are satisfied ; or, in other words, in 

 which there exists chemical saturation. 



Neither heat nor any of the other gelatinizing and swelling agents used (chloral 

 hydrate, chroinic acid, pjTogallic acid, ferric chloride, and Purdy's solution), except 

 probabl}^ chromic acid, causes any apparent notable degree of decomposition of the starch 

 molecule during the periods of observation; but they do change the raw starch into a 

 distinctl}' different constitutional form by altering the intermolecular arrangements. The 

 individuality in the behavior of the chromic acid, coupled with its pecuharities, leads to the 

 belief that the first effect of this reagent is a constitutional transmutation, as above stated, 

 which is probably followed by a series of oxidation processes. No doubt more or less de- 

 composition is brought about sooner or later by pyrogallic acid and ferric cliloride, both of 

 which substances are in concentrated solution; but with Purdy's solution the decomposi- 

 tion, if any, that may be caused by the small amount of alkaline hydrate present need not 

 be considered. It is manifest from this that these methods of gelatinization represent essen- 

 tially a group of a number of different groups of chemical methods which are available for 

 the study of the changes in the starch molecule and its dcri^'atives through all of thieir 

 ramifications of changes of constitution and decomposition to the ultimate CO2, HoO, etc. 



Doubt may exist as to whether or not the primary objects of the research would not 

 have been better accomplished by a study of a less number of specimens by a larger num- 

 ber of methods, especially by methods akin to those emploj^ed by Fischer and his pupils 

 in the separation and identification of stereoisomers, and by Cross and Bevan in the study 

 of cellulose. But this alternative plan, for certain reasons, was practically impossible; and, 

 as regards the one adopted, it was believed that a few methods would be sufficient to elicit 

 such fundamental differences as might be necessary in a preliminary investigation, and that 

 the larger the number and variety of starches the better the idea of what is to be expected 

 from the really serious research that must follow. Then again, it might seem that a study 

 of a large number of members of a single genus, or of representatives of quite a number of 

 genera of only a single family, might be sufficient as an index of what is to be anticipated 

 in other corresponding groups; but the wisdom of the plan adopted of examining in a 

 number of instances, as in Liliacece, Amaryllidaceoe, and Iridacece, representatives of a 

 dozen or more genera, and as in Lilium, Narcissus, and Iris quite a number of species 

 and varieties, is clearly shown by the records. And it is also evident that the examination 

 of representatives of scattered families and genera has brought fruitful results. 



ASSISTANTS AND SOURCES OF SUPPLY OF MATERIAL. 



The very exacting demands upon the head of one of the most important departments 

 of a first-class medical school, and the enormous amount of labor required in an investi- 

 gation of this character, made it necessary for the author to assign certain laborious and 

 routine parts of the work to assistants. At the inception of the research it was believed 

 by the writer, who is not a botanist, that the best results were to be obtained by the con- 

 stant assistance of an expert botanist. To this end an arrangement was made with the 

 late Dr. Louis Krautter, instructor in physiological botany in the University of Penn- 

 sylvania, but whose tragic and lamentable death occurred before the investigation had 

 been started. The author secured the material, laid down the methods and lines of inves- 

 tigation, directed the work, and made the photomicrographs which accompany the histo- 

 logical and polariscopical descriptions, but the routine laboratory studies of the properties 

 of the starches were of necessity but regretfully assigned to assistants. Nearly all of this 



