where the single lines between the (C18)- residues represent B-carbonyl linkings, and the double lines two carbinol linkings. H. Brown's last publication, with Glendinning, is upon the velocity of diastase hydrolysis, and he finds that it does not follow the law of mass action. A. J. Brown has obtained a similar result in the case of invertin. Before passing to the next polysaccharide, the other sugars which have been said by different investigators to be products of diastase hydrolysis might be enumerated. Some observers have supposed glucose to be a product, but the conditions of the experiment were probably the cause of this observation, other enzymes being present in the diastase solution. Nasse has obtained a sugar which he calls ptyalose, differing from both glucose and maltose, by the action of ptyalin upon starch. The action of diastase upon starch is considered by Arthur Meyer as catalytic, the amylose taking up the elements of water and breaking up into two or more molecules of amylodextrin, which subsequently forms dextrin and isomaltose; maltose is formed by intramolecular rearrangement from isomaltose as well as from dextrin. From the foregoing it will be seen that very many theories have been advanced by many workers to explain the hydrolysis of starch by diastase. Two facts, however, stand out clearly from the mass of complicated results: firstly, the production of maltose; and secondly, the production of a dextrin much more difficult to convert into maltose, but eventually convertible. Intermediate between the starch and maltose many dextrins, no doubt, are formed, and they have been named with the various terms enumerated above. Of these, Brown's maltodextrin only has been prepared in anything like a state of purity; but this may possibly be the simplest of them, as its constitution has been determined: the other dextrins are no doubt mixtures of several of the intermediate ones, and have not yet been prepared in such a state of purity that their properties could be established. Opposite is a table showing schematically the various results which have been obtained. SCHEME OF THE RESULTS OF THE HYDROLYSIS OF STARCH. but simultaneously. Griessmayer 1871-72 Brücke Ditto Ditto : erythrodextrin, O'Sullivan Ditto Two dextrins one coloured brown, one not coloured, by iodine. Sugar. Ditto ; but identical-> maltose. Erythrodextrin, and 3 achroodextrins. Maltose at each stage. 8 possible dextrins. Maltose at each stage. 1 erythrodextrin and 3 achroodextrins. Maltose. Ditto. Starch soluble starch erythrodextrin ➡achroodextrin → maltodextrin Dextrin and maltodextrin → maltose . Same results as above, but starch molecule larger than originally supposed. 2 dextrins → dextrins of smaller molecular weight→ maltose. 2 amylodextrins one quickly to sugar. one slowly to sugar. Starch dextrins → maltose. Dextrins =a and B amylo-, erythro-, achroo- dextrins. Dextrin and maltodextrin -> maltose. Maltose, with difficulty. Starch → amylodextrins (simplest amylogen) → maltodextrins + maltose. Glucose + isomaltose simpler glucodextrins grenzdextrin + maltose. achroodextrin. CHAPTER II. CHANGES IN THE POLYSACCHARIDES.-Continued. THE next polysaccharide, inulin, which is also found as a reserve material in certain plants, undergoes hydrolysis by the action of the ferment known as inulase, discovered by Reynolds Green in 1887. The formula C12H20O10.2H2O is usually given to this polysaccharide, which, according to Bourquelot, is converted by fermentation into lævulose or fructose. Kiliani, from results of combustion, gave the formula. C36H62031 or 6C6H10O5 + H2O to this carbohydrate; but Brown and Morris, in 1889, from determinations made by Raoult's method, considered the formula to be 2C36H62O31. They also stated that inulin resembled amylodextrin in its properties very closely, and they gave the following formula to express its constitution :— ((C12H22O11)2) which is closely analogous to that of amylodextrin. The ultimate products of hydrolysis of inulin are different, and they therefore thought that the amylin and amylon groups in its molecule were different to those in amylodextrin, because lævulose is obtained, whereas in the latter case maltose is obtained. Also, that it is a product of the hydrolysis of an unknown carbohydrate, and stands in the same relation to this body as amylodextrin does to starch. According to Düll, the molecular weight of inulin is 2950, which agrees with the formula (C6H1005)18 or (C6H10O5)18+ H2O; this observer has found that the lævulins obtained from inulin by acid hydrolysis are really reversion products of lævulose, and therefore they are not hydrolytic decomposition products. In animals, carbohydrates are stored up in the form of glycogen; this reserve material is found in greatest amount in the liver, where it is converted into maltose and glucose when required for use by the animal. The chemical changes which this body undergoes by the action of diastase have been investigated by Miss Tebb, who has compared this hydrolysis with that produced by acids. The former method gives achroodextrin and another dextrin named dystropodextrin, whilst dilute acids give soluble glycogen, erythrodextrin, and achroodextrin. The sugar formed is supposed to be maltose, from which, by the action of glucase, glucose is produced in the liver. Miss Tebb has identified her dystropodextrin with the product of the same name obtained from glycogen by Seegen. As regards the molecular weight of glycogen, the most recent determinations have been made by Jackson, who used carefully purified glycogen, and found that the amount of lowering of the freezing-point corresponded to a molecular weight of 9500-10,000. Caroubin, a polysaccharide of the formula C6H10O5, has been obtained by Effront from the seeds of the carob-bean |