5.8.
SI-RO-FLEX ULTRAMICROTOME
145
where advanced work is being performed. The design features particularly
favor the production of the best possible sections. However, since the
instrument is cycled by hand, this inevitably lacks the precision of a motor
drive, and no doubt limits the uniformity of serial sections.
I have had only a very limited experience with this microtome, and
cannot speak with much authority about it. It should not get out of order
easily. The only serious fault that I have found with its design is the
problem of adjusting the cutting speed by reaching into the dashpot with
a screw driver. Obviously this cannot be done while the instrument is
actually in operation, nor can one know exactly how much change he is
going to make in speed when he makes a small change in the position of
the adjustment screw. Thus, this microtome has certain very decided
advantages, but these are coupled with some disadvantages that make it
an unlikely choice for some types of work.
5,8. SI-RO-FLEX Ultramicrotome
This microtome is available from the Schuco Scientific Division of
Schueler and Co., 75 Cliff Street, New York 38, New York. The microtome is based on the design of J. L. Farrant and S. E. Powell. The
particular feature of this instrument is lateral stability. This is achieved
by having wide flat leaf-springs incorporated in the specimen arm which
allow it to move and bend in a vertical axis only. It was the conviction
of the originators of this microtome that irregular section thickness
resulted mainly from uncontrolled lateral excursions of the block along
the knife edge as sections were being cut. This, of course, might not be
a factor if the knife edge always was oriented truly at right angles to the
arc made by the specimen arm, but in practice this would be fortuitous.
No doubt lateral instability can be regarded as a problem in the original
Porter-Blum microtome, but probably this need not be regarded as a
serious limitation with most of the other newer instruments. In special
cases, with particularly wide or hard blocks, the extreme lateral stability
of the SI-RO-FLEX microtome might be significant.
The specimen is advanced by thermal expansion produced by heat
radiated from two incandescent filament lamps. The rate of advance is
varied by altering the applied voltage to the lamps by means of a variable
transformer. The microtome is equipped with a motor drive, offering a
choice of three speeds. However, the drive is at a uniform rate so that
SI-RO-FLEX ULTRAMICROTOME
145
where advanced work is being performed. The design features particularly
favor the production of the best possible sections. However, since the
instrument is cycled by hand, this inevitably lacks the precision of a motor
drive, and no doubt limits the uniformity of serial sections.
I have had only a very limited experience with this microtome, and
cannot speak with much authority about it. It should not get out of order
easily. The only serious fault that I have found with its design is the
problem of adjusting the cutting speed by reaching into the dashpot with
a screw driver. Obviously this cannot be done while the instrument is
actually in operation, nor can one know exactly how much change he is
going to make in speed when he makes a small change in the position of
the adjustment screw. Thus, this microtome has certain very decided
advantages, but these are coupled with some disadvantages that make it
an unlikely choice for some types of work.
5,8. SI-RO-FLEX Ultramicrotome
This microtome is available from the Schuco Scientific Division of
Schueler and Co., 75 Cliff Street, New York 38, New York. The microtome is based on the design of J. L. Farrant and S. E. Powell. The
particular feature of this instrument is lateral stability. This is achieved
by having wide flat leaf-springs incorporated in the specimen arm which
allow it to move and bend in a vertical axis only. It was the conviction
of the originators of this microtome that irregular section thickness
resulted mainly from uncontrolled lateral excursions of the block along
the knife edge as sections were being cut. This, of course, might not be
a factor if the knife edge always was oriented truly at right angles to the
arc made by the specimen arm, but in practice this would be fortuitous.
No doubt lateral instability can be regarded as a problem in the original
Porter-Blum microtome, but probably this need not be regarded as a
serious limitation with most of the other newer instruments. In special
cases, with particularly wide or hard blocks, the extreme lateral stability
of the SI-RO-FLEX microtome might be significant.
The specimen is advanced by thermal expansion produced by heat
radiated from two incandescent filament lamps. The rate of advance is
varied by altering the applied voltage to the lamps by means of a variable
transformer. The microtome is equipped with a motor drive, offering a
choice of three speeds. However, the drive is at a uniform rate so that