1008 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



(C^H^On), which is readily soluble in water and gives with iodine a reddish- 

 brown color. Erythrodextrin is converted into (3) Achroodextrin, (C 12 H 2u O 10 ) ff 

 + H 2 O, or (C lt S K O w \.C lt R n O n , which is likewise very soluble, tastes slightly 

 sweet, but gives no coloration with iodine. Achroodextrin now breaks up 

 into (4) Isomaltose, which through change in configuration is transformed to its 

 isomere (5) Maltose. 



Products similar to these are formed by the various diastatic ferments in 

 the body, and in addition also some dextrose. Ptyalin l acts rapidly on starch, 

 producing dextrin and maltose, but very little dextrose. Amylopsin, from the 

 pancreas, acts still more rapidly than ptyalin, and with the production of con- 

 siderable dextrose. The diastatic ferment of intestinal juice acts very slowly 

 on starch, forming dextrin, maltose, and a little dextrose, while the ferment in 

 blood-serum likewise acts slowly but with complete transformation of all the 

 maltose and dextrin formed, into dextrose. 



The above facts lead Hamburger to suggest that the diastatic ferments of the body 

 consist of mixtures, in different proportions, of diastase, which forms dextrin and maltose 

 from starch, and of glucase, which converts these into dextrose. This, however, is merely 

 an hypothesis, and glucase has never been prepared. The vegetable diastase is not iden- 

 tical with that found in the body. Thus ptyalin, like emulsin, breaks up salicin into sali- 

 cylic alcohol and dextrose, of which action vegetable diastase is incapable. But ptyalin, 

 again, is not identical with emulsin, for it will not act on amygdalin. 



Glycogen, or Animal Starch. Recent investigations have shown that in 

 all the particulars of diastatic decomposition glycogen is identical with vege- 

 table starch. 2 Glycogen is soluble in water, giving an opalescent fluid. The 

 blood has a normal composition which does not greatly vary. After a hearty 

 meal excess of fat is deposited in fatty tissue, excess of proteid in the muscular 

 tissue, while excess of sugar is stored in the muscles and especially in the liver- 

 cells in the less combustible and less diffusible form of glycogen. About one- 

 half of the total quantity of glycogen is found in the muscles, the remainder 

 in the liver, where it may even amount to 40 per cent, of the dry solids. 

 When the blood becomes poor in sugar, the store of glycogen is drawn upon to 

 such an extent that in hunger the body becomes glycogen-free. Muscular work 

 likewise causes the rapid conversion of glycogen into sugar. The sources of 

 glycogen are certain ingested carbohydrates, and also the dextrose derived from 

 proteid. If large quantities of proteid be fed, glycogen may be stored. If 

 milk-sugar and galactose be burned in the cells of an otherwise starving animal, 

 the dextrose from proteid is economized and glycogen is found. If dextrose 

 or levulose (or anything which produces dextrose, e. g. cane-sugar, maltose) be 

 fed, there is a direct conversion of the sugar into glycogen. Voit 3 has called 

 attention to the fact that only directly fermentable sugars are convertible into 

 glycogen. Cremer 4 shows that yeast-cells contain much glycogen when cul- 

 tivated in media which they ferment, not, however, when cultivated in milk- 



1 See Hamburger : Pfluger>s Archiv, 1895, Bd. 60, p. 573. 



2 Kiilz and Vogel : Zeitschrift filr Biologic, 1895, Bd. 31, p. 108. 

 8 Zeitschrift fur Biologic, 1891, Bd. 28, p. 270. 



4 Ibid,, 1895, Bd. 31, p. 188. 



