CONCLUDING EEMARK8. 161 



Section Cutting. — Sections of infested leaves, stems, 

 roots, etc., may be cut either by hand with a hollow- 

 ground razor, or with the microtome. When cut by hand- 

 the Specimen is imbedded in a soft cork or a piece of pith. 

 The razor is dipped in dilute alcohol and then drawn 

 diagonally across the piece of pith (containing the speci- 

 men) with a steady sweep. Before cutting each section 

 the razor should be dipped in dilute alcohol. " Great care 

 is required, in cutting sections by hand, to hold the razor 

 firmly yet lightly, so as to cut them thin and at the same 

 time even, and this cannot be done without a great deal of 

 practice." A much easier method of cutting sections is 

 by using a microtome. Zeiss's microtome is everything 

 that could be desired for cutting vegetable sections. It 

 consists of a round glass plate, borne by two pillars on a 

 heavy brass foot, on which the knife or razor is worked 

 by hand. The specimen to be cut is imbedded in a brass 

 tube and pushed up through an opening in the plate by a 

 screw with divided head. The divisions of the head indicate 

 the thickness in hundredths of a millimetre =0'03937 inch. 

 Hardening Vegetable Sections. — As it is neces- 

 sary to harden many vegetable substances, this can be 

 done by placing them in dilute alcohol (1 part water to 2 

 parts methylated spirit). The materials to be hardened 

 should be left in this mixture about 24 hours, then trans- 

 ferred to pure methylated spirit for about 12 hours, when 

 they are ready for cutting and mounting. 



Mounting Sections. — Microscopic sections are 

 usually mounted on glass slides (3x1 in.), either dry or 

 immersed in some fluid, and covered by a thin glass slip. 

 Small animal parasites may be quickly killed by immers- 

 ing them in alcohol ; after a time take them out, dry 

 them, and, if transparent, they may be at once mounted in 



M 



