SCIENCE. 
i87 
tend to explain what the directive agencies are or how they 
work — one thing, at least, is plain : that if a very few ele- 
mentary substances can enter into an untold variety of 
combinations, and by virtue of this variety can be made to 
play a vast variety of parts, this result can only be attained 
by a system of mutual adjustments as immense as the vari- 
ety it produces, as minute as the differences on which it de- 
pends, and as centralized in direction as the order and har- 
mony of its results. And so we come to understand that 
the unity which we see in Nature is that kind of unity 
which the mind recognizes as the result of operations sim- 
ilar to its own — not a unity which consists in sameness of 
material, or in identity of composition, or in uniformity of 
structure, but a unity which consists in similar principles of 
action — that is to say, in like methods of subordinating a 
few elementary forces to the discharge of special functions, 
and to the production, by adjustment, of one harmonious 
whole. 
And of this unity, we who see it, and think of it, and 
speak of it — we are part. In body and in mind we belong 
to it, and are included in it. It is more easy to admit this 
as a general proposition than really to see it as truth and to 
accept all the consequences it involves. The habitual atti- 
tude of our thoughts is certainly not in accordance with it. 
We look on “ Nature ” as something outside of us — some- 
thing on which we can look down, or to which we can look 
up, according to our mood ; but in any case, something in 
which we are exceptions, and which we can and ought to 
regard from an external point of view. It may be well, 
therefore, to consider a little more carefully “ Man’s place 
in Nature” — his share and position in that unity which he 
sees and feels around him. 
AN IMPROVED MICROTOME. 
By Wm. Hailes, M.D., Professor of Histology and Path. Anat., 
• Albany Medical College. 
This instrument is designed especially for use in the 
working laboratories of our medical schools and colleges, 
where large numbers of sections are required for micro- 
scopical examination. 
It may be employed as a simple instrument or as a freez- 
ing microtome, arranged for ice and salt — ether spray, , 
rhigoline, etc., etc. 
The employment of ice and salt (coarse) is preferred, be- 
cause it costs but little and freezes the mass solidly and 
quickly, and, if desired, 500 or 1000 sections can be ob- 
tained in a few moments’ time of freezing is about seven 
minutes, except in very' warm weather when it requires a 
few moments longer. 
The instrument does not work so satisfactorily in warm 
weather, owing to the rapid melting of the surface of the 
preparation. It is absolutely necessary that the mass 
should be frozen solid, or the sections cannot be cut 
smoothly. 
An extra freezer may be employed, and while one speci- 
men is being cut the other may be frozen, and by exchang- 
ing cylinders (they being interchangeable), no delay is 
necessary to its continuous operation. 
The art of cutting is readily acquired, and when the pre- 
paration is frozen it is the work of a few moments to obtain 
several hundred sections. Two hundred sections, or 
more, if desired, can be made each minute, and of a uniform 
thickness of about 7^5 of an inch (thinner or thicker, from 
about 73V5 inch to about riu inch, according as pointer is 
set). See explanation of cut No. 1. The delivery, ease 
and rapidity with which they can be cut. must be seen in 
order to be appreciated. It is not necessary to remove the 
sections from the knife every time, but twenty or thirty may 
be permitted to collect upon the blade; they lie curled or 
straighten themselves out perfectly in the course of a few 
hours. The knife I employ is an ordinary long knife from 
an amputating case. Perfectly fresh tissues may be cut 
without any previous preparation, using ordinary mucilage 
(acaciae) to freeze in, but most specimens require special 
preparation. If preserved in Muller’s fluid, alcohol, etc.. 
Fig. 1. — Poly-microtome (without freezing apparatus). A, small well, 
fitting on pyramidal bed-plate ; B, pyramidal bed-plate containing 
different sizes ; C, micrometer screw ; D, ratchet-wheel attached to 
screw • E, lever actuating the micrometer screw by means of a pawl 
engaging in teeth of ratchet-wheel ; F, arm carrying a dog, which 
prevents back motion of screw j G, regulator for limiting the throw of 
lever, and consequently governing the micrometer screw ; H, lever nut 
for fixing regulator; I, index, with pointer and graduated scale, from 
74^0 u t0 u * nc ^ » K, knife for cutting sections ; L, knob to turn 
micrometer screw direct when pawls are detached ; M, table, clamp; T, 
table cf microtome, with glass top to facilitate cutting. 
Fig. 2. — A, 15 , tube containing specimen which is surrounded by freezing 
mixture in tin receiver C, D ; E, F, revolving hopper with wings ; W, W, 
for stirring the ice ; G, outlet for melted ice. 
they require to be washed several hours in running water ; 
then, according to the suggestion of my friend, Dr. David 
J. Hamilton, F. R.C. S., etc.,* University of Edinburgh, 
Scotland, the specimen is placed ina strong syrup (sugar, two 
ounces ; water, one ounce), for twenty-four hours, and is 
removed to ordinary mucilage acacia; for forty-eight hours, 
and is then cut in the freezing microtome. 
The sections may be kept indefinitely in a preservative 
fluid: 1 } glycerins, § iv ; aqux destil § iv ; acidi carbolici 
gtt, iij ; boil and filter. (Dr. Hamilton). The addition of 
alcohol, § ij, is advisable. 
* See ‘ k A New Method of Preparing Large Sections of Nervous Cen- 
tres for Microscopical Investigation .”— Journal of Aunt, and Phys ., Vol. 
XII. 
