TROD UCTS OF DIGESTION OF ST I RCH. 395 
well-differentiated substances have been described. The first step in 
the action is, according to all observers, 1 the formation of soluble starch 
(amigdulin, amidulin, amidogen, or amylodextrin). This substance is 
rapidly formed, usually in one or two minutes; it givea the same blue 
reaction with iodine as raw starch or starch paste, and is precipitated by 
tannic acid, by which it is distinguished from the dextrins formed in the 
subsequent stages. 
In the second stage, this soluble starch is decomposed into a sub- 
Btance giving a red colour with iodine and maltose. The substance 
giving the red colour now gets the name given by Briicke of erythro- 
dextrin; it corresponds to Nasse's dextrin. Griessmayer's dextrin-1 
and Bondonneau's dextrin-a. 
In the third stage, this erythrodextrin is split up into a dextrin (or 
several dextrins). giving no coloration with iodine, and hence called 
achroodextrin, and a further quantity of maltose. Finally, according to 
some, a part of this achroodextrin breaks up, yielding more maltose, 
and a variety of achroodextrin, altogether unaffected by diastatic 
ferments, which with the maltose split off at different stages from the 
intermediate products, forms the final product of the reaction, no matter 
how long prolonged. 
These successive changes may be represented as in the following 
scheme : — 
Starch 
I 
Soluble Starch 
I I 
Ervthrodextrin Maltose 
I I 
Achroodextrin Maltose 
All observers are agreed as to the existence of soluble starch, and 
practically all as to that of erythrodextrin, although Museums and Meyer 2 
state that, on carefully mixing dextrin stained with iodine, with soluble 
starch stained with iodine, they obtained the colour of erythrodextrin, and 
conclude that what has been called ervthrodextrin is probably such a mixed 
colour. This result has not been confirmed by other observers ; still it 
should be borne in mind that a pure substance has not yet been isolated, and 
that at present erythrodextrin is only a name given to a substance supposed 
to exist, because of a red colour which is obtained at a certain stage in the 
digestion of starch by diastatic enzymes. The material which is found later 
in the process, which is not a sugar and gives no coloration with iodine, has 
been called achroodextrin, but it has none of the constant properties of a 
pure simple substance, and is probably a mixture of several substances 
(achrobdextrins), though as yet none of these have been properly isolated. 
Musculus and Gruber, 3 working on starch solutions with dilute acids and 
with diastase, differentiated, according to varying conditions of temperature, 
amount of diastase added, and length of time of action of the ferment, three 
achrobdextrins (a, (3, and y), possessing, according to these observers, different 
1 Xasse, Arch. f. d. yes. Physiol., Bonn, 1S77, Bd. xiv. S. 474 ; Griessmayer, Chcm. 
Centr.-BL, Leipzig, 1871, S. 686; Briicke, " Yorlesungen," and Sitzungsb. d. k. Akad. d. 
Wissensch., AVien, 1872, Abth. 3; Bondonnean, Compt. rend. Acad. d. Sc, Paris, I s 7"'. 
tome lxxxi. pp. 972, 1210; Husculus, Ztschr. f. physiol. Ghent., Strassburg, 1878, Bd. ii. 
S. 177. 
-Ztschr. f. physiol. *'/ ., - --'>urg, 1880, Bd. iv. S. 4. r >l. 
3 Ibid., 1878, Bd. ii. S. 177. 
