Microtomes : their Choice and Use 241 



Sliding microtomes having an automatic feed arrange- 

 ment are not always to be recommended. The automatic 

 attachment may be so constructed as to restrict the range 

 of thicknesses otherwise available. The cutting of sections 

 of extreme thinness is not the chief feature to be looked 

 for in a microtome. The writer recently had occasion to 

 cut sections 250 /* thick; such an attainment would have 

 been impossible with certain microtomes. 



The Minot and other Microtomes by Zimmermann. 

 Another excellent instrument which has attained great 

 favour is Professor Minot's microtome for the paraffin 

 ribbon method. It is made more or less perfectly by several 

 makers, but was introduced by Zimmermann of Leipzig. 

 Fig. 63 illustrates this microtome without knife-holder or 

 object-holder. It is worked by rotating the balance wheel K, 

 whose rotary action is changed into a vertical movement 

 of the object-slide by means of a crank action D. When 

 the object-slide is moving upwards, a lever H strikes one 

 of the spokes of the ratchet-wheel G, which in turn moves 

 the large-toothed wheel B of the horizontal micrometer 

 screw, thus advancing the object towards the knife. 



There are several forms of this instrument made by Zim- 

 mermann ; the most useful for general work is Model II., 

 capable of giving sections of from 1 to 20 microns thick ; 

 that is to say, when the worker knows how to sharpen the 

 knife to such perfection as is required for sections 1 micron 

 thick. This remark, of course, applies to all microtomes. It 

 must be understood that this microtome is not an all-round 

 instrument such as the Thoma, Becker, or Schanze models. 

 It works with great rapidity ; it cuts sections up to 2 by 

 2 inches with exactness, and absolutely flat. The orienta- 

 tion of the object is easily arranged. Its only fault is that 

 it is not compensated for wear and tear, so that in time it 

 will require to be returned to the maker or a skilled 

 mechanic for adjustment. 



The Reinhold-Giltay Microtome. Another microtome 

 of great ingenuity constructed for the paraffin process is 



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