12 Smith, on a Dissecting Microscope. 
rests let down and when not in use — and it is made complete 
as a box by a piece of wood (similar to that forming the back) 
No. 2. 
: 1 
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which drops into a groove in front of the drawer and is fastened 
by small hooks at the top to the stage, and upon this piece the 
condenser can conveniently be fixed by catches when the 
instrument is packed up I have thought it better to make 
this front a separate part, as it might sometimes be found very 
much in the way if permanently fixed on by hinges. I have 
not shown it in the drawing, thinking it unnecessary to do so. 
Drawing No. 2 also shows the small dark tube devised by 
Dr. Carpenter, for facilitating dissection without the aid of 
the glasses, and described at page 192 of his work on the 
Microscope. This tube (the adding of which as a part of my 
apparatus I am indebted to him for suggesting) has a piece 
of ground glass fitted into the bottom, and can either be used 
for the purpose more immediately intended, or for softening 
the light, which is often very necessary when working at night 
with a lamp or candle. 
As a fitting addendum to the description of my microscope, 
I may here give that of a modification of the ordinary dis- 
secting trough, suggested to me by Professor Busk, who has 
kindly permitted me to add it to my paper. The new trough 
is made by cutting a small piece (say for example one inch 
long and a quarter of an inch in width) out of the centre of 
a gutta-percha one, and inserting in the hole thus left a piece 
of glass, so as to be on a level with the surface ; by this 
arrangement, the object to be dissected, after being cut open, 
can be fastened down over the glass by pinning it to the 
gutta percha on either side, and in this way it can be illumi- 
nated either by the condenser or the mirror, as may be 
