1914] LAND—TEMPERATURE CONTROL 523 
deep was made to take in the knife and to permit about 1 cm. of the 
knife to project. A nipple at each end of the trough serves to 
attach small rubber tubes (fig. 1). The ends of the trough should 
be soldered to prevent leaking on the microtome. Any microtome 
knife having a detachable handle can be used. A flexible safety 
razor blade may be used, provided the heads of the clamping screws 
are flush with the sides of the blade holder. 
A tank provided with a stopcock and Y-tube is placed above 
the microtome at a height which will insure a good flow of water. 
One tube of the ‘“‘Y”’ is attached to a tube of the object holder by a 
rubber tube of small caliber, the other to the nipple of the cooling 
trough. Tubes lead from the holder and from the trough to a waste 
receptacle. The tank is filled with water of the proper tempera- 
ture for the required thickness of ribbon. The block and knife 
reach the proper temperature for cutting soon after the water is 
turned on. The entire apparatus is shown in fig. 2. 
The apparatus was designed primarily for cutting very thin 
sections (2-4 u) of liverworts which had to be imbedded in soft 
paraffin, but it has been found useful when very thick sections 
(20-50 u) are wanted. In cutting the latter, the knife trough is 
detached, and the tank filled with warm water which is allowed to 
flow through the object holder only. The temperature of water 
necessary for cutting sections of various thicknesses is easily 
determined by experiment. 
UNIVERSITY oF CHICAGO 
