ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
809 
dehydrating. The chromic acid seems to fix the protoplasm, and 
macerate the cellulose, allowing the alcohols to pass more freely. I 
allowed the specimens to remain in the several per cents, of alcohol 
from two to twenty-four hours, according to their size and texture. As 
a rule, I found that the more gradually the specimens were dehydrated 
the better. From absolute alcohol, the specimens were placed in a 
solution of equal parts turpentine and paraffin. The solution con- 
taining the specimens was then raised gradually from a temperature of 
20° C. to about 45° C. They were then placed in melted paraffin, kept 
as nearly at 50° C. as possible. Small specimens will be permeated in 
one or two hours, but large specimens require from four to six hours. 
From the 75 per cent, alcohol I placed the specimens in a stain. 
The stains I tried were alum-cocliineal, hsematoxylin, fuchsin, methyl- 
green, methyl-blue, methyl-violet, and ammonia-carmine. I found 
alum-cochineal a good stain for fungi, plumules, stems, roots, and root- 
tips, but it would not penetrate the cucumber cotyledons. Fuchsin 
would penetrate anything I tried ; but as it is soluble in alcohol, it is 
necessary to overstain the specimens, and then allow the colouring to 
come out until it is about right. Haematoxylin stained all the tissue 
that I tried except the young cucumber cotyledons. This stain gives 
large specimens a dark blue colour on the outside, and a purplish-pink 
colour on the interior. The nuclei and the cell-walls are brought out 
clearly. I did not have good success with the methyl colours, as they 
were easily dissolved out by the alcohol. 
If specimens have not taken sufficient colour, or if the alcohol has 
removed too much of the colour, sections can be stained upon the 
slide, after they are cut. Any stain can be used, but none that I tried 
differentiated the parts sufficiently. Fuchsin will give enough colour 
in a few seconds. The sections must stand in haematoxylin from two to 
ten minutes, and in alum-cochineal from ten to twenty minutes. If it 
is intended to stain upon the slide, an alum fixative will be found better 
than collodion. 
I heated the slides in the gas-flame to melt the paraffin, and poured 
on turpentine to wash it out. The specimens were then mounted in 
balsam dissolved in chloroform. Air-bubbles that appear when sections 
are first mounted, will disappear after the slides stand a few hours. If 
the razor or knife used for cutting is very sharp, small specimens may 
be cut 1/2500 or even 1/5000 in. in thickness. But larger specimens 
cannot be cut more than 1/600 to 1/1500 in. thick without crowding 
the tissues together and giving them the appearance of being shrunken.” 
Preparing, Preserving, and Mounting Objects of Natural History 
for the Microscope.* — Mr. N. Pike says his own method of procedure in 
selecting, preparing, and preserving small delicate specimens (excepting 
eggs) is as follows : — 
“ I first procure the most perfect live specimens and drop them in 
strong alcohol, and let them remain about twenty-four hours. This not 
only instantly destroys life without injuring the objects, but also 
hardens them a little. They are then taken from the alcohol and 
placed in small narrow tubes, which I have for this purpose, just large 
The Microscope, x. (1890) pp. 266-8. 
