90 ' Tue Microscope. 
3 
fluid, and add a drop of a solution of acetate of potash of the 
following strength: Acetate of potash, 1 oz.; Water, 4 oz. 
Cover and fasten it with a ring of varnish, if it is desired to 
preserve it. The advantages are the simplicity and beauty of 
the results obtained ; it is also good for exhibiting the structure 
of cartilage. 
A Goop STAIN FoR SPINAL Corb, ETc.—A solution of Hama- 
toxylin prepared with water and alcohol. The sections are 
kept immersed in it during an hour, and the temperature is 
maintained between 40° and 50° O. — 104° to 122° Fahr. They 
are then removed from the solution, washed and placed for 3 
hours in a 2 per cent. alkaline solution (Borax), or in one of 
potassium ferricyanide. Afterwards they are submitted to the 
influence of alcohol, xylol, and Canada balsam, in the usual 
manner. 
CorROsIVE SUBLIMATE FOR BRAIN, ETC.—After the prepara- 
tion has been hardened in Miiller’s fluid, instead of putting it in 
alcohol, place it for some days in a 5 per cent. solution of cor- 
rosive sublimate, which is renewed every day until the solution 
is no longer colored. If left too long the preparation becomes 
black, or if not long enough small black points appear. It is 
very elastic and firm, and very thin sections can be cut ; it stains 
very well without ammonia, carmine, ete. 
IRIDESCENCE OF Fiy’s Wines.—I do not think Mr. Tuffen 
West’s explanation of extreme thinness more than half ac- 
counts for the iridescence of the wings of a fly. The color is 
certainly not due to scales, as suggested by another member. 
Anyone who has blown soap bubbles will remember that their 
iridescence only appears in all its splendor when they are ea- 
tremely thin ; when first blown, and when the film is (compar- 
atively) thick, the iridescence is slight. Now, these wings are 
thicker than the film of a soap-bubble; consequently they 
ought not to be iridescent. I have seen it stated, and from my 
own observation I believe that the statement is correct, that in- 
sects’ wings are composed of two membranes. These may 
sometimes be partially separated, and when a wing is stained 
the staining fluid will get between the two membranes. Now, 
the fact that these two membranes touch one another is suf- 
