522 BOTANICAL GAZETTE [JUNE 
In this laboratory the practice has been to cool the knife and 
block with lumps of ice. This method, while in the main giving 
good results, is unsatisfactory for the finest sectioning. Water 
usually gets on the ribbon and does damage; also great care is 
necessary to keep the microtome from rusting. 
The various difficulties were in a large measure overcome as 
Fic. 2.—Apparatus for temperature control, showing all attachments 
follows: The face of the ordinary circular metal object holder, 
which comes with all microtomes of the better class, was turned out 
to form a cup. A plate of thin brass was soldered over the cup, 
making a new face for the object holder, and turned down to the 
original diameter of the disk. Two holes were drilled and tapped 
at opposite sides of the disk and two short tubes for attaching small 
rubber tubes were screwed in. Fig. 1 shows this disk in the clamp 
of the microtome. 
For controlling the temperature of the knife, a trough of thin 
metal—tin, brass, or copper—about 20 cm. long and about 2 cm. 
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