TOOLS AND METHODS OF WORK 17 



THE "FLATTERS" MICROTOME. 



The microtome is made of brass, the tube or well is 3in. deep by lin. 

 in diameter internally, the spindle is of the same length, the screw 

 having twenty-eight threads to the inch. The spindle is fitted with a 

 thumb-screw at the lower end to admit of the toothed discs being easily 

 changed. A spring stop, the tension of which can be adjusted, works 

 in the teeth of the disc, thus ensuring a series of sections of uniform 

 thickness. Three discs, divided as follow, are found to be sufficient for 

 ordinary purposes, viz. : — 



No. I. 72. teeth, giving sections TtniTrin. in thickness " 

 No. 2. 54 ,, ,. Twoin. 



No. 3. 43 „ „ wTD-in. 



Approximately. 



The latter being the one mostly employed for general purposes, and 

 which when moved two notches gives sections woin. in thickness. 

 Numbers i and 2 are used chiefly for the production of sections of 

 animal tissue and of textile fibres. To ascertain the thickness of the 

 sections obtained, multiply the notches in the disc used by the number 

 of threads per inch on the spindle. 



The knife plate, 2f in by 4! in., is made of hardened brass polished 

 "dead flat," and has an aperture the same diameter as the tube, tapering 

 slightly to the top to prevent the specimen from turning or rising while 

 the sections are being cut; it is attached at one end to the headstock 

 by a stout screw, and is securely held in position by a reliable catch, 

 which is clamped under the headstock. The specimen to be cut is 

 placed in the well of the microtome and melted paraffin wax, melting 

 point 130 deg. F., poured in; this is allowed to set, and the superfluous 

 wax is then removed. The "candle" so formed is then moved upwards 

 by turning the toothed disc. The sections are cut by passing the knife 



