SECTION CUTTING. 



53 



h'\ 



111 using the instniment in this way, however, the piece of tissue 

 must he thin, not more than 5-7 mm. in thickness, or thereby. 



Gathcart's Freezing Microtome (fig. 34). The instrument is 

 screwed to a table by means of a clamp (C). Fix by means of gum 

 the tissue to be frozen, not more than i cm. thick, upon the zinc 

 plate. Fill the bottle with ether and put the spray apparatus 

 under the zinc plate. Work the spray apparatus until the mucilage 

 and tissue arc frozen. 



Sections are cut by means of a flat knife pushed along on the 

 glass supports (GG), 

 the tissue being 

 raised by the large 

 milled head placed 

 underneath (M). 



The sections are 

 removed from the 

 knife by means of 

 a camel's-hair pen- 

 cil, and placed in 

 water. 



Fig. 35 shows 

 Gathcart's micro- 

 tome clamped to a 

 table, and the 

 method of cutting 

 sections by means 

 of a planing iron. 

 The planing iron is 

 used in exactly the 

 same way as for Rutherford's microtome. 



Roy's Microtome (Freezing), Modified by Malassez (fig. 36). 

 This instrument is extremely convenient, the cutting instrument 

 being an ordinary razor.- Instead of ether, Malassez uses chloride 

 of methyl, which is preserved in a stout metallic flask. A stream 

 of the methyl chloride is directed against the under surface of the plate 

 on which the tissue to be frozen is placed. It freezes much more 

 rapidly than with ether. 



Cutting a Continuous Series of Sections in Paraffin. For this 

 purpose the "rocking microtome" (fig. 37) of the Cambridge 

 Scientific Instrument Company, or Minot's microtome, is most 

 useful. 



Embed the tissue in paraffin in the usual way ; place the razor in 

 position, and fix the embedded tissue to the end of the brass cap on 

 the, horizontal bar. Move the brass cap, with its adherent em- 

 bedded tissue, forwards, until it touches the knife-edge. The 



FIG. 35. Showing how to use a Planing Iroii for 

 Cutting Sections. 



