HOW TO USE THE MICROSCOPE 



31 



oven (Fig. 31) should not be much higher than the melting- 

 point of the paraffin. 



The specimen is now ready to be embedded. First make a 

 mould of cardboard or a lead-embedding frame (Fig. 32), melt 

 the paraffin, and then place the 

 specimen in a manner that will 

 facihtate cutting. Remove the 

 excess of paraffin and cut when 

 desired. 



In using the collodion method 

 for embedding fibrous speci- 

 mens, as wood, bark, roots, etc., 



the specimen is first fixed with picric acid, washed with water, 

 cleared in ether- alcohol, embedded successively in two, five, 

 and twelve per cent ether-alcohol collodion solution, and finally 

 embedded in a pure collodion bath. 



Fig. 32. — Paraffin Blocks 



CUTTING SECTIONS 



Specimens prepared as described above may be cut with a 

 hand microtome or a machine microtome. 



HAND MICROTOME 



In cutting sections by a hand microtome, it is necessary to 

 place the specimen, embedded in paraffin or held between 

 pieces of elder pith, carrot, or potato, over the second joints 

 of the fingers, then press the first joints firmly upon the speci- 

 men with the thumb pressed against it. If they are correctly 



Fig. 33. — Hand Microtome 



held, the specimens will be just above the level of the finger and 

 the end of the thumb, and the joint will be below the level of 

 the finger. 



Hold the section cutter (Fig. t,_^) finnly in the hand with 



