This microtome presents all the advantages of any plan heretofore
employed in hardening animal or vegetable tissues for section cutting,
while it has many advantages over all other devices employed for the
same purpose.
Microscopists who are interested in the study of histology and pathology
have long felt the necessity for a better method of freezing animal and
vegetable tissue than has been heretofore at their command.
In hardening tissues by chemical agents, the tissues are more or less
distorted by the solutions used, and the process is very slow. Ether and
rhigolene have been employed with some degree of success, but both are
expensive, and they cannot be used in the presence of artificial light,
because of danger of explosion. Another disadvantage is that two persons
are required to attend to the manipulations, one to force the vapor into
the freezing box, while the other uses the section-cutting knife.
The moment the pumping of the ether or rhigolene ceases, the tissue
operated on ceases to be frozen, so ephemeral is the degree of the cold
obtained by these means.
The principal advantages to be obtained by the use of this microtome
are, first, great economy in the method of freezing, and, second,
celerity and certainty of freezing. With an expenditure of twenty-five
cents, the tissues to be operated on can be kept frozen for several
hours at a time.
[Illustration: FREEZING MICROTOME.]
Small objects immersed in gum solutions are frozen and in condition for
cutting in less than one minute.
The method of using this microtome can be understood by reference to the
illustration. A represents a revolving plane, by which the thickness of
the section is regulated, in the center of which an insulated chamber is
secured for freezing the tissue. It resembles a pill-box constructed of
metal. A brass tube enters it on each side. The larger one is the supply
tube, and communicates with the pail, a, situated on bracket, s, by
means of the upper tube, t. To the smaller brass tube is attached the
rubber tube, t b, which discharges the cold salt water into a pail
placed under it. (See b.) The salt and water as it passes from pail, a,
to pail, b, is at a temperature of about zero. The water should not be
allowed to waste. It should be returned to the first pail for continual
use, or as long as it has freezing properties. As a matter of further
economy, it is necessary to limit the rate of exit of the freezing
water. This is regulated by nipping the discharge-tube with the spring
clothes pin supplied for the purpose. Should the cold within the chamber
be too intense, the edge of the knife is liable to be turned and the
cutting will be imperfect. When this occurs the flow of water through
the chamber is stopped by using the spring clothes-pin as a clip on the
upper tube. In order to regulate the thickness of the tissue to be cut
a scale is engraved on the edge of the revolving plate, A, which,
in conjunction with the pointer, e, indicates the thickness of the
section.--_Microscopical Journal_.
* * * * *
THE ST. GOTHARD TUNNEL.--It appears that the traffic through the
St. Gothard Tunnel has increased, since the inauguration of through
international services, to such an extent that the Company have already
obtained sanction for laying the second pair of rails in the tunnel. The
Great Eastern Railway Company has increased its steamer traffic, and
built additional station accommodation at Harwich.
* * * * *