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Reconstruction in low relife on sheet celluloid or gelatin.

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Department of Aimtomy, Belleme Medical College, New Pork 17niaer.Tity
It is usual for more reconstructions to accumulate during
the course of a morphogenctic study than it is desirable to
reproduce. This appears to be inevitable, but the time spent
in purely technical work and the perishability of plastic reconstructions are serious disadvantages. I have tried during
the past two years t o reduce these disadvantages to a minimum bv using a modificatioii of the glass-plate technique, in
which sheet celluloid or sheet gelatin is substituted for glass.
Eecoiistructions made with these materials share with those
made on glass the limitation of requiring to be viewed perpendicularly to the plane of section in which the embryo has
been cut. Their comparative lack of depth does not interfere
seriously with their intelligibility and for purposes of reproduction it is a positive advantage, for the outlines can
readily be traced. Provision for viewing the reconstruction
in its true proportion may be made by alternating drawings
on the thinner material with glass plates of appropriate
thickness, although I have never found it necessary to use
such a proccdure.
In order that the edges of the glass plates used in an ordinary glass reconstruction may coincide exactly, a preliminary
drawing is required to be made on paper and subsequently
oriented and traced. The comparative simplicity of registering consecutive drawings made directly on sheet celluloid OF
gelatin, which, if necessary, can be trimmed afterward with
scissors, reduces the technical procedure to a minimum. A
series of drawings made on such sheets and attached in serial
ordcr constitutes a reconstruction more quickly madc and as
insti*uctivefor many purposes as those prepared by the currently used plastic and graphic. methods. The reconstructions are casily stored and are practically imperishable.
Sheet celluloid may be bought from the Eastmaii Kodak
Co. 8 s Transparent Kodaloid no. 1,in sheets 0.002 inch thick.
Similar material 0.005 iiicli or thicker is supplied by tlie same
firm, but bechomes too opaque when many sheets are used. It
may be used conveniently for many othcr purposes, however,
wliich do iiot entail superimposing too many sheets. The
expense of the thinner material (twenty-five cents per square
foot) led me to invcstigatc the qualities of the thin sheet
gelatin commoiily used f o r wrapping candy boxes. This is
iiifcrior to celluloid in that it tears rathcr easily and that
wetting it must be avoided. Rut with ordinary precautions it
gives vcrp satisfactory results.
A cwwatcly rectangular sheets of celluloid or gelatin are first
cut to the required size. F o r this pnrpose, I place the matcrinl over a large piece of ‘beaver board,’ markcd with conveniently spaced lincs aiid cut with a sharp kiiifc guided by
a metal squarc. The ordinary cardcutter is.apt to let tlic
material slip, thus distorting the angles. India ink does not
mark well on a greasy surface, and sheets fiiigercd in cutting
should be wiped with cz cloth moisteiied in 95 per cent alcohol.
Trouhle in this regard may he avoided by wearing cotton
gloves while cutting.
For drawing, a projection microscope is most coiiveniciit.
The first section is centcred and a sheet of the material placed
011 a drawing-board small enough to bc moved easily within
tlie space available. The drawing-board is then moved until
the projected image of the section falls in the correct position
oil the sheet. To hold tlie sheet firmly on tlic board, fiat lead
below with pieces
~veightsof various sizes are I ~ R C C covered
of inner tire-tube. Sheet lead and rubber map 1)c made to
adliere by means of tlie thick sliellac commoiily used in
garages. The required structures in the first section are now
drawn upon the sheet in India ink with a thin pen, and the
projected image of a second section is accurately superimposed upon the drawing of the first. This can quickly be
done by moving the drawing-board until the drawing of the
first section fits the projected image of the second. A small
metal square is then fitted around two adjacent sides of the
first sheet, which is numbered, removed, and replaced exactly
by a second sheet. After the projected image of the second
section has been traced on the second sheet, the image of a
third section is made to fit the drawing of the second, \vhich,
in its turn, is numbered and removed; the procedure being
repeated until the drawings have been finished. It will be
found convenient to arrange the section numbers on the sheets
with a view to their simultaneous visibility after the drawings have been superimposed in order.
The section to be placed at the bottom of the finished reconstruction is now put on a white sheet of paper. The drawing
of the next section of the series is then oriented carefully upon
it, and the two sheets attached along one edge so that they
may remain separate like the pages of a book. Another sheet
of paper is placed between the drawings and a third section
oriented on the second, and so on, until the entire series of
sheets has been attached in one or several batches. For attaching celluloid sheets, amyl acetate or acetone are more
easily controllable when thickened with collodion and cause
less wrinkling of the sheets. To attach gelatin sheets, I lap
a moistened strip of paper (of the required length and about
inch wide) along one edge of the lower sheet during the
orientation of the second drawing. The paper is then removed and the part of the upper sheet over the place it previously occupied is pressed down upon the first. This method
causes wrinkling of the gelatin, and some of the sheets are
apt to separate when dry. To avoid subsequent separation,
the moist edges of the whole batch of united sheets should be
clamped tightly together while drying. There is room for
improvement in the present method f o r attaching sheets.
1)ifiercntial coloring, jf desired, is preferably finished or
well started before the sheets are attached, though it is often
convenient to finish it afterwml. The collodion paints on
tlic market, such as Duco or Valspar lacquer, dry quickly
a i d have no tendciicy to peel. Transparerit water colors
wrinkle gelatin slieets aiid, sooner or later, peel off celluloid,
as do the oommercial colored inks unless applied in thin lines
with a pen. Brnshcs used for coloring ma)- he passed through
the corks of small vials of acetone or amyl acetate far enough
to Beep their bristles immersed. These can be withdrawn
from the vials and dipped into paint as required, a separate
brush being used for each color.
Several variations of the different steps of the method liavc
been tried. I n its present form and as applied 10 celluloid, it
was demonstrated at the Ann Arbor meeting of the American
Association of A11atomists, in April, 1928.
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low, sheet, relife, celluloids, reconstruction, gelatin
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