PHILADELPHIA 
LARGE LABORATORY MICROTOME— DESCRIPTION, 
The object clamp is carried on an arm which is fitted to a slide in the carriage 
and is constructed with special reference to convenience of manipulation. 
The arm carrying the entire object clamp is arranged to slide vertically in a 
groove in the front of the slide piece, allowing the object to be rapidly elevated 
or depressed with reference to the knife, regardless of the position of the micro- 
meter screw. 
The feed arrangement is by micrometer screw, working in an adjustable block 
in the lower part of the carriage, and acting on the base of the slide piece. The 
screw is cut with the utmost care and accuracy, the pitch of the threads being 
0.5 mm. The disk of the micrometer screw is graduated to 500 parts. On the 
margin, notches are cut of such size that one notch corresponds to two of the 
divisions on the disk. 
Feed mechanism. The method of regulating the thickness of sections offers 
advantages not possessed by any microtome of similar type. It is readily set 
for thickness and the motion is definitely limited, thus permitting the successive 
cutting of sections to any extent without variation in thickness and without 
being dependent upon an audible click or reading the graduation, although 
permitting the latter if desireH. By this arrangement the whole attention can 
be given to the cutting proper, thus obtaining much more perfect results, 
especially in serial and very thin sectioning, and saving a great deal of time. The 
finest feed is 2 micra. 
Feed Mechanism of Large Laboratory Microtome 
41 
