FORMATION OF CRYSTALLINE BODIES IN COLLODION. 25 
time since brought to me for microscopic examination, a 
specimen of collodion or ethereal solution of gun-cotton, 
desiring to know if it was crystalline in its constitution as has 
been asserted. 
The gun-cotton from which the collodion had been made 
was prepared by Mr. Parrish, by means of pure nitric and 
sulphuric acids, according to the formula given by him in 
some "Observations on Collodion," in the last number of this 
Journal, page 290. 
The specimen, as presented to me, was about one ounce in 
quantity, contained in a glass-stoppered vial, was viscid, 
perfectly clear, and without sediment. Upon examination 
with the microscope, we could detect nothing, even with a 
power of 1200 diameters, except a finely and faintly granular 
constitution. The bottle remained upon my table for four 
weeks, when, upon examining it accidentally, I observed a 
deposite of a whitish flocculent matter at the bottom, and 
passing in various directions through the supernatant liquid 
numerous very long, delicate, acicular, shining crystals. 
Some of these were full an inch in length. Upon submitting 
them to the microscope, I found them to be transparent, 
highly refractive, hexahedral prisms, with truncated or 
pyramidal summits, measuring from the 1.6000th inch to the 
1.857th inch in diameter. Very many of the larger crystals, 
near the extremities only, enclosed bubbles of liquid collodion, 
as represented in fig. c. 
The flocculent sediment consisted of some undissolved 
cotton fibres, some very fine fragmentary filaments of the 
same, a few fine starch granules, vegetable epidermoid cells, 
a few spiral vessels, spiral fibre cells, and numerous crystalline 
bodies. Among the latter were many regular octahedrons, 
the largest of the perfect ones measuring at the sides l-882d 
inch; when larger than this two or more of the angles were 
truncated. Some of the largest of the latter measured as 
much as 1.397th inch. Four-sided prisms with pyramidal 
3 
