■ A Universal Microtome. 289 



moving parts is small the speed of cutting can be regulated 

 instantly, or the object can be stopped even while a section is 

 being cut. 



These considerations lead us to think that a continuous rotation 

 of a handle is not the best method of giving the reciprocating 

 movement of the object in a microtome, and we have adopted a 

 similar design to that used in the Eocking Microtome. Many 

 years' experience have shown that this movement of the hand is 

 convenient and the mechanism is simple and efficient. A radial 

 bar which can turn about a vertical axis at one end is made to 

 oscillate backwards and forwards through a large angle by means 

 of a handle fixed at its other end. This oscillation moves the 

 object past the knife and feeds it upward at the end of the return 

 stroke, the feed occurring after the object has completed its 

 travel. 



The foregoing considerations would lead one to expect that 

 with very little skill good sections can be cut with this microtome, 

 and we find that this is the case. We also believe that with objects 

 which are difficult to cut, the fact that the force exerted by the 

 knife on the object is directly transmitted to the hand will enable 

 an operator to make the best use of his skill, and may there- 

 fore enable him to get better results than would otherwise be 

 possible. 



The amount of feed for giving any required thickness of section 

 is set instantly and requires no clamping. Each division on the 

 scale corresponds to 1 micron in thickness, and sections as thick 

 as 35 microns can be cut. 



The feed or micrometer screw is fitted with a milled head 

 which permits of very ready fine adjustment of the object to the 

 knife. The manipulation of the orientating object holder is simple. 

 The object (see fig. 3) is clamped in a vice B, which has a cylin- 

 drical stem C sliding in a cylindrical hole in the sphere D. The 

 sphere is cut almost completely through along the axis of the hole, 

 and the screw E which clamps it also serves to clamp the stem of 

 the object holder, owing to the geometrical mounting, at whatever 

 angle the sphere may be in its seating. To orientate the object 

 the clamping screw is slackened, and the object can then be 

 rotated in any direction through an angle of 16° from the vertical, 

 owing to the movement permitted to the sphere. It can also be 

 rotated through any angle about a vertical axis, and can be raised 

 or lowered owing to the movement of the stem in the sphere, and 

 then rigidly clamped by the single screw. 



The knife holder is easily adjusted to give a slicing cut ; it can 

 also be moved so that sections can be cut with new parts of the 

 knife as it becomes blunt or damaged. The knife thus requires 

 less frequent sharpening, much time is saved, and good work can 



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