892.] 



THE MICROSCOPE. 



155 



rections, adapted to the square stage of my instrument as illus- 

 trated by the engraving accompanying*. The stage-plate of the 

 microscope is altered by a triangular groove along the whole 

 length of the lateral margin, and by an enlargement of the central 

 aperture. Into this a heavy diaphragm may be slipped with an 

 opening of the usual size for the Abbe condenser. 



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en 



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The apparatus for mechanical movement is essentially the ordi- 

 nary mechanical stage, but working directly by hand instead of 

 by rack and pinion, the especial advantage being the free long 

 movement thus permitted. It is in two parts ; a rectangular 

 frame (see a, e, and ^") , the lateral bar of which is beveled to 

 fit into the triangular groove in the side of the stage plate, in 

 which it slides forward and backward ; and a thin plate (3 and 

 /) longer than the preceding and a little narrower, its beveled 

 edges sliding laterally in a V-shaped groove on the inner edges 

 of the anterior and posterior bar of the frame just mentioned. 

 The projecting ends of this plate serve as hand-rests in dissecting. 

 Three small screw^s are set in it as stops for the slide, and 

 the knobs by which it is moved are bored in the centre as 

 sockets for the stage forceps. Its central opening is of the 

 same size as the larger opening in the stage-plate, and in this 

 rests loosely a circular piece of glass (c), on wdiich a dish may 

 be set in examining small alcoholics. This apparatus, when well 

 fitted and smoothly ground, works with a nicety and precision 



*In this cut the larger figure shows the stage from above, the front edge uppermost; the 

 figure to the right gives an^end view'; and the lower one a view from behind. 



