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 5oC. 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 and 7oC. 

 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- 



