PRODUCTS OF DIGESTION OF STARCH. 397 



(achroodextrin). If, when this stage is reached, the solution is rapidly 

 cooled and neutralised, a little maltose can be separated from accompany- 

 ing dextrose, showing that maltose is here also formed, but is con- 

 verted rapidly into grape-sugar. 



Although maltose is the chief sugar formed in the action of both 

 ptyalin and amylopsin upon starch, yet a trace of grape-sugar is also 

 formed. 1 The quantity of grape-sugar formed is in both cases small, but 

 is greater in the case of the pancreatic ferment. It has recently been 

 discovered that in both salivary and pancreatic digestion, besides 

 maltose and small quantities of grape-sugar, another sugar, isomaltose, 2 

 is formed, in considerable quantity. The relative quantity of the three 

 sugars varies with the quantity of ferment present, and the duration of 

 the experiment. A weak ferment and short time of action favour the 

 formation of isomaltose; by much ferment and prolonged action large 

 quantities of maltose are produced, accompanied by traces of dextrose. 3 

 It is stated that traces of an inverting ferment are present, both in the 

 salivary and pancreatic glands, especially the latter ; and it is possible 

 that the traces of dextrose formed may be due to the action of these on 

 the maltose and isomaltose first formed. 



The action of the amylolytic enzymes on glycogen is precisely similar 

 to their action on starch ; dextrin, maltose, and isomaltose being formed 

 in very much the same proportions. 4 



The production of maltose by the diastatic ferments is not the end 

 of the digestion of amyloses; there is evidence that maltose never 

 reaches the systemic circulation. If it be injected intravenously it is soon 

 discoverable in the urine ; 5 this shows that in digestion it is inverted, 

 either before it is absorbed, or after absorption and before reaching the 

 systemic circulation. 



This further process of hydrolysis may be to some extent carried out, 

 so far at least as concerns that portion of maltose arising from 

 salivary digestion, by the hydrochloric acid of the gastric secretion, but it 

 is mainly brought about by an inverting ferment, discovered by Brown 

 and Heron in the mucous membrane of the small intestine, and also in 

 the succus entericus. 6 



The succus entericus (as well as the intestinal mucous membrane and 

 glycerin or water extracts of it) possesses only a feeble diastatic action 



1 Musculus and Gruber, Ztsclir. f. physioL Chem., Strassburg, 1878, Bd. ii. S. 177 ; 

 Musculus and von Mering, ibid., 1878, Bd. ii. S. 403 ; von Mering, ibid., 1881, Bd. v. S. 

 185 ; Brown and Heron, Ann. d. Glum., Leipzig, 1879, Bd. cxcix. S. 165 ; 1880. Bd. cciv. S. 

 228 ; Proc. Roy. Soc. London, 1880, p. 393. 



2 Kiilz u. Vogel, Ztschr. f. Biol., Miinchen, 1894, Bd. xxxi. S. 108. The existence of 

 isomaltose is, however, denied by Brown and Morris (Trans. Chem. Soc., London, 1895, vol. 

 Ixvii. p. 737), who state that it is a mixture of maltose and dextrins. 



3 Journ. PhysioL, Cambridge and London, vol. xv.; Abelous, Compt. rend. Soc. de biol., 

 Paris, 1891. 



4 Hensen, Verhandl. d. phys.-med. Gesellsch. zu Wurzburg, 1856, Bd. vii. S. 219 ; 

 Virchow's Archiv, 1857, Bd. xi. S. 395 ; Claude Bernard, Gaz. med. de Paris, 1857, No. 13 ; 

 J. Seegen, Oentralbl. f. d. med. Wissensch., Berlin, 1876, S. 849; Arch.f.'d. ges. PhysioL, 

 Bonn, 1879, Bd. xix. S. 106 ; Kitlz u. Vogel, Ztschr. f. Biol., Miinchen, 1894, Bd. xxxi. 

 S. 108. 



5 Bimmemunn, Arch. f. d. ges. PhysioL, Bonn, 1879, Bd. xx. S. 201; Philips, 

 Jahresb. ii. d. Fortschr. d. Thier-Chem.. Wiesbaden, 1881, Bd. xi. S. 60 ; Dastre et Bour- 

 quelot, Compt. rend. Acad. d. sc., Paris, 1884, tome xcviii. p. 1604; Bourquelot, Journ. de 

 t'anat. et physioL, etc., Paris, 1886, tome xxii. p. 161. 



6 Brown and Heron, Proc. Roy. Soc. London, 1880, p. 393; Ann. d. Chem., Leipzig, 

 1880, Bd. cciv. S. 228; Vella, Untersuch. z. Naturl. d. Mensch. u. d. Thiere, 1881, Bd. 

 xiii. S. 40; Bourquelot, Compt. rend. Acad. d. sc., Paris, 1883, tome xcvii. p. 1000. 



