8 
METHODS IN PLANT HISTOLOGY 
across it and the next section is damaged even before it is cut. The 
side of the knife next the object should be wiped with the finger, 
theoretically after every section. It is very inconvenient to wipe 
the knife in a rotary microtome. Another advantage of the sliding 
type is easy to feel but difficult to describe: In the rotary micro¬ 
tome the stroke is so automatic that there is little room for skill, but 
in the sliding microtome, with one’s hand on the sliding block, little 
variations in the stroke, variations which become instinctive, give the 
expert a control not yet attained in the rotary forms. 
Amateurs, and even professional botanists who have little 
aptitude in the use of machines, had better rely upon the rotary 
microtome. However, no better comment on the comparative merits 
of the two forms could be given than the practice of an expert tech¬ 
nician in our own laboratory, who uses a rotary microtome when 
making sections for ordinary class work, but who turns to a sliding 
microtome of the Jung-Thoma pattern when cutting sections for 
his own research. 
A much-improved rotary microtome, devised by Dr. H. N. Ott, 
president of the Spencer Lens Company, combines the precision and 
stability of the sliding microtome with the convenience of the rotary. 
Its effectiveness depends, in large measure, upon the simple but rigid 
clamp for holding the object. The same firm has also produced a 
very rigid sliding microtome, embodying features suggested by Pro¬ 
fessor It. B. Thomson, of the University of Toronto. The stability, 
which makes such a microtome desirable for cutting sections of hard, 
woody structures, is an advantage in cutting very thin sections of 
material imbedded in paraffin. 
Microtome knives are available everywhere and, when perfectly 
sharpened, are unsurpassed. Those who sharpen knives for sur¬ 
geons can grind out nicks, but they do not know how to sharpen a 
microtome knife and they cannot be taught; they sharpen knives for 
Dr. Carver and Dr. Cutterout. 
In recent years several clamps have been devised to hold the 
blade of the Gillette safety razor, the hard, even edge of which is 
very satisfactory for microtome sections. After dealers had ignored 
our suggestions, Mr. A. W. Strickler, at our request, devised the form 
of holder 1 shown in Figure 4. It is made of brass and can be used in 
either rotary or sliding microtomes. The sectional view shows that 
1 At 1320 East Fifty-seventh Street, Chicago, Illinois. 
