Busk on Starch- Granules. 
63 
not when it has nearly or completely terminated.* This ex- 
pansion or dissection of the granule is effected by M. Martin 
by means of heat applied in an ingenious but still incon- 
venient way, while the object is under the microscope. He 
thus employs it : — 
" Between two very thin glasses, of the same size as the 
stage of the microscope, a little amylum, with a sufficient 
quantity of water, is to be put, and the former well spread out 
with the finger, to prevent as much as possible the formation 
of bubbles. The number of amylum grains in the field of 
view should not exceed ten or fifteen. The glasses should 
lie freely on the spring-piece, which must be raised by means 
of two pieces of cork introduced below it, so that while the 
two glasses are lying right upon the object-bearer, a current of 
cold air will ascend from below, or permit the little flame to 
continue burning in the hole of or below the stage. As the 
glasses are wide, they protect the microscope from too great a 
heat or other danger. The small flame is to be obtained from 
a common thread, doubled and slightly waxed. This, when 
ignited, gives a flame quite sufficient to boil the amylum." 
In the course of his experiments he discovered that the 
slightly iodizing of the starch-grains delayed, so to speak, the 
entire process of boiling, and rendered the result more certain 
and satisfactory, and he states that his process seems to succeed 
still better in a concentrated solution of alum, with as much 
tincture of iodine as will colour the grains of a steel blue. 
The same benefit arises also in my process from the addition 
of as much iodine as will render the starch a pale blue without 
destroying its transparency ; and the use of iodine in either 
case is attended with the further advantage that it renders the 
starch in its subsequently changed condition much more visible 
than it otherwise would be. 
Instead of heat I employ concentrated sulphuric acid, and in 
the following way; — A small quantity of the starch to be 
examined is placed upon a slip of glass and covered with five 
or six drops of water, in which it is well stirred about, and 
with the point of a slender glass rod the smallest possible 
quantity of solution of iodine is applied, which is to be quickly 
and well mixed with the starch and water. As much of the 
latter as may be must be allowed to drain off, leaving the 
moistened starch behind, or a portion of it is to be removed by 
inclination of the glass, and the starch is then to be covered with 
a piece of thin glass. The object must then be placed in the 
* Vide Observations on the Structure of the Starch-granule in a paper 
on Valisneria spiralis, by E. J. Quekett, published in the third number 
of the ' London Physiological Journal ' in 1844. 
