148
5.
SECTIONING
category. It relied upon thermal expansion to advance the block, and
mechanically the most complicated part of it was its bearing system.
Clevenger (1963) may be said to have started with that instrument and to
have simplified it further, particularly by eliminating the rear bearings.
This he was able to do by designing his specimen support arm in such a
way that it had sufficient flexibility for the necessary movements. In this
respect it resembles the design of Sitte (1955). One does not buy a
Clevenger microtome. He makes it himself!
Clevenger's microtome is designed to be made with hand-tools, although
a circular saw and a drill press would be desirable. Its frame is of wood.
Its metal parts can be cut out with a hack saw and soldered as necessary.
Where screw threads are required, commercially available materials can
be adapted. Aside from perhaps 2 days of labor, there is no reason why
the microtome need cost more than $5.00.
The investigator using Clevenger's microtome would cycle the instrument by hand while a lamp bulb was placed near the specimen
support rod so that thermal expansion advanced the specimen. The
instrument is so designed that the resting position of the specimen
support rod is below the level of the knife edge. Thus, to initiate a cycle,
one has to lift the specimen rod above the knife edge. As this is done it is
deliberately deflected laterally so that the specimen bypasses the knife in
being lifted. The specimen rod then is brought in contact with a vertical
guide, and released. The elastic tension of the support rod and gravity
then sweep the specimen past the knife. It would seem likely that this
must produce an undesirably rapid cutting speed. However, I see no
reason why this could not be reduced and controlled very simply by
adding a dashpot mechanism, as is found in the Cambridge microtome
(Chapter 5.7.). Perhaps a spring opposing the fall would work as well.
Of course it is not likely that laboratories regularly involved in ultrathin sectioning would wish such a simple microtome, lacking the conveniences and reliability available in commercial instruments. Nonetheless,
if an investigator needed only occasional sections, or wanted a training
instrument at nominal cost, this microtome could be a reasonable
solution. One can suppose, also, that it might be used effectively for
preparing material for phase contrast microscopy without involving the
investigator in heavy expense.
5.
SECTIONING
category. It relied upon thermal expansion to advance the block, and
mechanically the most complicated part of it was its bearing system.
Clevenger (1963) may be said to have started with that instrument and to
have simplified it further, particularly by eliminating the rear bearings.
This he was able to do by designing his specimen support arm in such a
way that it had sufficient flexibility for the necessary movements. In this
respect it resembles the design of Sitte (1955). One does not buy a
Clevenger microtome. He makes it himself!
Clevenger's microtome is designed to be made with hand-tools, although
a circular saw and a drill press would be desirable. Its frame is of wood.
Its metal parts can be cut out with a hack saw and soldered as necessary.
Where screw threads are required, commercially available materials can
be adapted. Aside from perhaps 2 days of labor, there is no reason why
the microtome need cost more than $5.00.
The investigator using Clevenger's microtome would cycle the instrument by hand while a lamp bulb was placed near the specimen
support rod so that thermal expansion advanced the specimen. The
instrument is so designed that the resting position of the specimen
support rod is below the level of the knife edge. Thus, to initiate a cycle,
one has to lift the specimen rod above the knife edge. As this is done it is
deliberately deflected laterally so that the specimen bypasses the knife in
being lifted. The specimen rod then is brought in contact with a vertical
guide, and released. The elastic tension of the support rod and gravity
then sweep the specimen past the knife. It would seem likely that this
must produce an undesirably rapid cutting speed. However, I see no
reason why this could not be reduced and controlled very simply by
adding a dashpot mechanism, as is found in the Cambridge microtome
(Chapter 5.7.). Perhaps a spring opposing the fall would work as well.
Of course it is not likely that laboratories regularly involved in ultrathin sectioning would wish such a simple microtome, lacking the conveniences and reliability available in commercial instruments. Nonetheless,
if an investigator needed only occasional sections, or wanted a training
instrument at nominal cost, this microtome could be a reasonable
solution. One can suppose, also, that it might be used effectively for
preparing material for phase contrast microscopy without involving the
investigator in heavy expense.