40 THE AMERICAN MONTHLY [Feb 
A New Freezing Apparatus for Microtomes. 
Our readers will remember a carbonic-acid refrigerat- 
ing apparatus for microtomes which we described in our 
last issue. An ether apparatus for the same purpose, 
used by Dr. Albert Noll, of Jena, consists in evaporating 
ether in a vacuum in order to produce the necessary cold 
for freezing through the desired objects. 
The apparatus is constructed as follows: A brass cham- 
ber, on whose upper surface lies the object that is to be 
cut, serves for the reception of the ether. This, Dr. Noll 
has used for some time on a Schanze microtome. The 
bottom of this chamber is 4 to 2:6cm. thick, the top 2°5 to 
2cm. The height is 3cm. A shaft serves to fasten it to 
the microtome. On two adjoining sides of the chamber 
thereare two tubes. The apparatus is connected by pipes. 
The first pipe leads to a gas funnel, with stop-cock, and 
through this the ether is filled. The second leads to an 
exhaust apparatus, preferably a water-suction pump, 
which clears the chamber and provokes the evaporation 
of theether. Thelatter must be of thick material; the 
other should be of thin material. Having fastened the 
chamber of the microtome and attached the pipe, the fun- 
nel is filled; its tapis then shut with a certain quantity of 
ether. The funnel is then raised above the level of the 
chamber, the funnel tap opened, and the ether allowed to 
flow into it. The tap_is shut, the funnel laid aside, and 
the exhaust apparatus set in motion by opening the water- 
cock. As a consequence, a vacuum is created up to the 
funnel tap and the ether evaporates. After about a 
minute there is sufficient cold developed to freeze an object 
lying in the chamber. With the dimensions of the cham- 
ber as given, and the full quantity of ether, the frost 
will last fifteen minutes. If it is desired to stop the 
operation in order to begin cutting, or to fill in fresh 
ether, open the funnel-tap and shut the water-cock. 
