HOW TO USE THE MICROSCOPE 



35 



The cutting surface consists of two separated but parallel glass 

 benches. The object is held by a clamp and is raised by a 

 micrometer screw, which, when moved through one division by 

 turning the divided head, raises the specimen o.oi mm. 



The sliding microtome has a track of 250 mm. The object 

 is held by a clamp and its height regulated by hand. The disk 

 regulating the micrometer screw is divided into one hundred 

 parts. When this is turned through one division, the object is 

 raised 0.005 min - or 5 microns, at the same time a clock-spring 

 in contact with teeth registers by a clicking sound. If the disk 

 is turned through two divisions, there will be two clicks, etc. 

 In this way is regulated the thickness of the sections cut. When 

 the micrometer screw has been turned through the one hundred 

 divisions, it must be unscrewed, the specimen raised, and the 

 steps of the process repeated. The knife is movable and is 

 drawn across the specimen in making sections. 



The base sledge microtome (Fig. 36) has a heavy iron base 

 which supports a sliding-way on which the object-carrier moves. 



Fig. 36. — Base Sledge Microtome 



The object-carrier is mounted on a solid mass of metal, and is 

 provided with a clamp for holding the object. The object is 

 raised by turning a knob which, when turned once, raises the 

 specimen one to twenty microns, according to how the feeding 

 mechanism is set. 



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