26 
PHARMACEUTICAL BOTANY 
Pour fluid off and add pure melted paraffine and repeat 2 or 3 times 
until rid of all trace of xylol. A tray is then prepared by taking a 
piece of paper and folding up its edges all around to the height of 
about a half inch. Half fill this on a cool surface with melted para¬ 
ffine. Heat two dissection needles in bunsen flame and with these 
dispose pieces of material in orderly fashion over, the crust which has 
by this time formed at the bottom of the tray. Blow upon the sur¬ 
face of the paraffine to harden it more quickly and as soon as the 
surface crust will bear it, plunge the tray into cold water. The 
material can now be left imbedded in paraffine until required for 
sectioning. 
If cutting is to be done in a cool room, softer grades of paraffine 
with melting points between 40° and 5o°C. should be used for 
imbedding. If on the other hand cutting is to be done at summer 
temperatures, the harder grades melting at between 55 0 and yo°C. 
should be employed. 
TECHNIQUE OF SECTIONING AND MOUNTING MATERIAL IMBEDDED 
IN PARAFFINE 
Strip off the paper tray from the imbedded material and cut out a 
block of paraffine containing the object which is to be sectioned, 
taking care to include at least 2 or 3 mm. of paraffine on all sides 
beyond the specimen. Take a segment of pine wood about an inch 
long and with a surface at one end about % in. square and coat the 
square area with melted paraffine. Warm the paraffine on the piece 
of pine wood and quickly press the paraffine block containing the 
specimen into this melted paraffine in the desired position for cutting. 
Heat a dissecting needle and apply this all around the base so that 
the paraffine block is firmly sealed to the wood. Dip paraffine block 
in cold water to harden. Now trim the paraffine block with a sharp 
scalpel so that the faces form right angles with each other. Adjust 
the wood in the clamp of the microtome and the microtome blade 
so that the top of the paraffine block just touches the near surface 
of the microtome knife. Make certain that the knife edge and the 
two opposite faces of the paraffine block are perfectly parallel. Now 
trim the remaining two sides of the block close to the object. Adjust 
the automatic feed of the rotary microtome by moving dial to num- 
