74 
SCIENCE. 
same plane, the third from the ventral, the fourth 
from the dorsal extensions of the common nucleus. 
I would call attention to the fact that the average 
dimensions of the cell nuclei of the auditory nerve 
nucleus equal those of the motor nuclei of the me- 
dulla and cord, and exceed some of them, and that 
the same statement applies to the cells as a whole. I 
make this statement in view of the recent communi- 
cation of Dr. Mason before the American Neurologi- 
cal Association, though I do not claim to make it on 
the same basis of careful and extensive micrometric 
observations that his communication was based on, 
but on a general impression derived from repeated ex- 
aminations which I think are sufficient to determine 
palpable differences. 
The present preliminary report is taken from a 
communication made by me *o the Journal of Ner- 
vous Diseases for last J une, but I trust before long to j 
submit to your readers a more exhaustive and illus- 
trated record of this interesting and suggestive piece 
of cerebral anatomy. 
DRY “MOUNTS” FOR THE MICROSCOPE. 
BY PROFESSOR H. L. SMITH, HOBART COLLEGE, N. Y. 
II. 
In a former paper, Science No. 3, I made a few 
remarks upon this subject, and described the methods 
which I had found tolerably successful, viz.: the rings 
made of shellac and lampblack, and those punched 
out of gutta-percha tissue. The former appear to 
answer quite well, and the changes, if any, are very 
slight, yet I have, in a very few cases, observed a de- 
terioration after the lapse of a year or so, probably 
from imperfect manipulation. Although I have not 
myself observed any great change in the gutta-percha 
mounts, I am not certain that they will stand prolonged 
use with immersion objectives without injury. I have 
mounted many specimens of delicate test objects for the 
Messrs. Spencer, and they are decidedly of the opinion 
that the shellac ring is the better for durability, and I 
am informed by Mr. Gundlach that the gutta-percha 
ring will not stand cedar oil. Mr. Phin has suggested 
that in time the gutta percha tissue will disintegrate. 
I have not yet noticed this, and do not think it will 
happen under the cover of a “ mount ” especially if 
protected by a ring of cement subsequently applied. 
If, however, such disintegration does, in time, happen 
to the tissue, this will be a great objection to its use. 
I have found that the “tissue” becomes so charged 
with electricity by handling, and also by the punching, 
that it interferes seriously with the latter operation, 
and thus makes it necessary to place strips of the 
“ tissue ” on thin moistened strips of paper, and to 
punch out both at the same time. The preparation 
of the shellac rings by the turn table obliges one to 
keep on hand a large stock all the time to insure per- 
fect drying, and to have them always ready. I am 
obliged to have some 1000 or 1500 on hand in ad- 
vance, and this necessitates a considerable outlay in 
stock, which will not always be convenient for ama- 
teurs. For the above reasons I now propose a new 
process which appears to meet all the desired wants, 
and which combines the advantages of the shellac 
cement and the gutta-percha rings. 
The very simplicity of this process causes me to 
wonder why it was not thought of before. I take a 
sheet of thin writing paper, white or colored, and dip 
it into thick shellac varnish (shellac dissolved in 
alcohol), and hang it up to dry. When thoroughly 
dry it should have a good glaze of the varnish on it 
(different thickness of paper can be used according to 
depth of cell required). Out of this shellac paper I 
cut my rings, and these can be made in any quantity, 
and kept for any time. The process of mounting is 
simple. The slide is cleaned, and the flat paper ring 
placed in the centre ; on this the cover is placed, 
having the object dried on it, and the two are held 
together by the forceps and gently warmed; thisserves 
to attach the ring to the slide, and cover, at several 
points, so that the forceps may now be laid aside. 
The next step is to take a glass slip, (another slide), 
and laying this on the cover, to grasp the two slides at 
each end by the finger and thumb of the two hands, 
and pressing them tightly together, to warm the slide 
gently ; by looking at the ring obliquely, on the under 
side, one can tell at once, when all the air is pressed 
out, and the adhesion is complete between the cover 
and the ring, and also the ring and the slide, and they 
must be held together a moment or two to cool. If 
the lac is sufficiently thick on the paper the adhesion 
takes place quickly, and with moderate heat, and there 
will be no danger of breaking the cover, unless it has 
been warped in the process of warming, which will 
sometimes occur when very thin glass has been heated 
too much for the purpose of burning off the organic 
matter, or when the support is too small in diameter, or 
when it is not flat. I think I may be able to induce the 
leading opticians to manufacture this paper and also 
the rings for sale ; for special purposes the paper might 
be printed beforehand, so that, when mounted, the ring 
would show on the under side the name of the preparer, 
or of the object. I cannot conceive of anything more 
satisfactory than these rings. Many large objects 
which would be crushed if one used only the shellac 
rings made on the slide, by the use of the turn table, by 
the giving way of these by softening, and under the 
necessary pressure for attaching the cover, are per- 
fectly protected by the paper rings. I am satisfied 
that the balsam mounts will be much less frequently 
used, as soon as we can find some sure dry process. The 
diatoms, as a rule, show much better when mounted 
dry, and with whole frustules, exhibiting b'oth the side 
and the front view, also the mode of attachment, etc. 
The dry mounts are certainly to be preferred when they 
are desired for anything except pretty objects, and 
even for this latter purpose there is often a very great 
difference in favor of the dry mount. Although I have 
not used these shellac paper rings for any very great 
length of time, yet I can see no reason why they 
should not be equal to the simple shellac ring for dur- 
ability, and very much superior to it in other respects. 
