6o 
MORPHOLOGY OF THE CELL. 
envelopes. The internal organisation depends, in these cases, on a definite relation 
of the M^ater and the moTQGufe& of starch ; the stratification of a starch-grain dis- 
appears, like that of a cell-wall, when the water is removed from it [e. g. by evapo- 
ration or action of absolute alcohol, &c.), because the more watery layers then 
become similar to the less watery ones, and the difference of refractive power in 
the two ceases. In the same manner the stratification also disappears when the 
substance of the grain is rendered capable by chemical means (as dilute potash solu- 
tion) of absorbing large quantities of water; the denser layers absorb relatively more 
water ; they thus become similar to the more watery layers, and it is no longer possible 
to distinguish between them. 
Besides the differentiation in the proportion of water which is recognised in the 
form of stratification, there is also in every grain an increase from without inwards 
in the amount of water. This is. partly ascertained by the refraction, partly, by the 
regular decrease of cohesion from without inwards. If the water is removed from 
fresh starch-grains, fissures are formed which cross the layers at right angles; in the 
interior a cavity is formed from which the fissures radiate ; these become narrower 
outwardly, and are widest in the centre. From this it follows that on drying the 
greatest loss of water occurs in the interior, and that this regularly decreases towards 
the outside ; but it also follows that the cohesion of the layers is less in the tangential 
direction (at right angles to the fissures) than in the radial. This points to the con- 
clusion that within every layer the loss of water is greater in the tangential direction 
than in the radial. 
If the water be removed from a fresh s,tarch-grain or from one which has taken 
up as much as it can, it contracts; the moTooufo s. contained in it approach one another 
as their envelopes of water become thinner. A similar change takes place if the 
granulöse is removed from a grain ; the farinose-skeleton of the grain which remains 
is, although saturated with water, much smaller than the original grain. This possibly 
results from the fact that the moTocufbe; ■ now consisting only of farinose, possess less 
attraction for water, and, having thinner; envelopes, approach nearer ; the cause may 
however also be that the number of ^aotooutoc has diminished. 
(b) The Extraction of the Granulöse of starch-grains, leaving behind a skeleton of 
farinose, can be brought about in very different ways: — i. By maceration in saliva at 
an elevated temperature ; in the starch of Canna indica the extraction, according to 
H. von Mohl, is slow at 35°-40° C, but is accomplished in a few hours at 5o°-55° C. ; a 
lower temperature suffices for wheat-starch, a higher is required for that of the potato ; 
Nägeli gives in general 40°-47° C. 2. According to Melsens a similar extraction may also 
be effected by organic acids, diastase, and pepsin. 3. According to Nägeli it can be 
accomplished also by very slow action of hydrochloric or sulphuric acid which has been 
so diluted with water that it does not cause the starch-grains to swell. 4. According to 
Franz Schulze, the granulöse is extracted in from two to four days by a saturated 
solution of sodium chloride containing i p. c. of hydrochloric acid, at a temperature of 
60° C; the residuum, which perfectly exhibits the organisation of the starch-grain, 
amounted, according to Dragendorff, to 57 p. c. in potato-starch, 2-3 p. c. in wheat- 
starch. These skeletons are not coloured by iodine (Nägeh's preparation with sul- 
phuric acid after fifteen months' extraction), or they become copper-red, and in 
places where the extraction was not perfect, bluish. They do not swell in boiling 
water, /. e. do not form paste. At 70° C. the whole of the starch-grain, according to 
Mohl, is dissolved in saliva ; the skeleton produced at 40^-5 5° G. is, however, not affected 
by saliva at 70°. 
Within the living cell the starch may be dissolved in very different ways ; probably 
solution occurs mostly under the influence of protoplasm, or by the assistance of 
nitrogenous combinations in the cell-sap. Sometimes the solution begins, as in the 
extractions mentioned above, with the removal of the granulöse, the farinose remaining 
behind; but this often takes place only partially; the extraction proceeds in places 
