132 NATURALISTS’ ASSISTANT. 
It consists of a heavy oblong base about four by ten 
inches and about a quarter of an inch in thickness. Arising 
from this base is an upright plate ; on either side of these are 
“ways,” those on one side being horizontal and on the other 
slightly inclined. On the horizontal ones a carrier travels 
holding the knife, while on the other a second carrier is 
borne, moved by a screw. ‘This second carrier holds the 
embedded specimen. Its method of operation is as fol- 
lows : the embedded material is placed in the carrier which 
is moved forward and upward until it is high enough to cut. 
Then the knife is slowly but steadily drawn across the end of 
the embedded object. The knife is then returned, the screw 
turned the fraction of a revolution, and then another sec- 
tion cut. Of course the knife is to be constantly wet with 
alcohol. A valuable addition to this instrument may be made 
by having the object carrier mounted on a universal joint, thus 
permitting any desired inclination. Some sections of this 
model are made of wood and are good for nothing. 
Dr. Seiler’s microtome is well shown in the figure and 
needs no further description. It possesses this advantage 
over all others, that the knife has a drawing motion. 
Freezing microtomes are sometimes employed. ‘hese 
are generally of the Sterling pattern and have an attachment 
by which a considerable degree of cold may be obtained 
either by ice and salt or by ether spray. 
