124 THE Microscope. 
microtome has its legitimate place and will in all probability 
remain in constant use. There are advantages arising from the 
use of both fresh and hardened specimens, but as a rule the lat- 
ter will be found the more satisfactory. 
There are several patterns of freezing microtomes, some 
using ice and others ether. The ice-freezing microtomes work 
very nicely, only it is somewhat disagreeable to charge them, 
even when ice is plentiful. The ether microtomes give good 
satisfaction provided the instrument is furnished with good noz- 
zles. It is a pleasure to use one of these well-made instru- 
ments; while if poorly made, giving a coarse spray and using 
much ether, they become a source of great trial. 
Tissues that have been hardened after some of the methods 
already given are best cut by the aid of some microtome. The 
common well-microtome consists of a stout brass tube closed at 
one end and fixed at right angles at the other end into a smooth 
plate of brass, which should be covered with glass. <A disk of 
brass is fitted into the interior of the tube and is acted upon by 
a delicate threaded screw fastened to the base of the tube. By 
turning the milled head below the tube, the disk is raised and 
the section embedded in the tube raised with it. The micro- 
tome shown in the accompanying figure answers every pur- 
pose. It is well made, has a smooth glass cutting-plate, the 
diameter of the tube is of good size, the screw is well cut and 
has a graduated head. The upper surface of the plug has a 
groove in it to keep the embedding mixture from rotating as 
the sections are cut. 
There is one difficulty with this microtome as with nearly 
all the others. There is nothing to prevent the embedding 
mixture from becoming loosened from the surface of the plug 
and rising in the tube as the sections are being cut; although 
the groove is pyramidal in shape still it will not hold the par- 
affin firm enough to prevent this most annoying imperfection. 
This trouble can be remedied, however, by having a small hole 
drilled in the upper surface of the plug and by fastening in it a 
small screw with a broad flat head. 
This is the most useful form of microtome that can be pur- 
chased for anything less than ten dollars. If three times this 
amount can be expended then some form of a microtome 
