ZOOLOGY AND BOTANY, MICKOSUOPY, ETC. 



721 



wear and tear is almost nil, and the accuracy is unlimited. The regu- 

 larity of the carrier-track is also secured by means of the arrangement 

 of the device which keeps the bearer of the histological object vertically 

 over the engage-point of the driving-wheel. This orderly arrangement, 

 to which constructors have hitherto paid too little attention, avoids all 

 quivering which could influence the carrier. The orientation of the 

 object to be cut is easily and quickly accomplished by the application 

 of a special handle ABC, which is fastened in a circular-shaped groove 

 of the carrier E. With the help of this groove and the rotation of 

 the cylindrical object-holder C about its axis, the celloidin plug moves, 



Fig. 123. 



so that the object can be oriented without removal from the vertical line 

 over the engage-point with the driving-wheel. The motive system of the 

 micrometer screw removes all back-friction of the catch on the toothed 

 wheel, and thus excludes any possibility of back-action. The female 

 screw of the micrometer is movable, and of the ordinary type. A 

 special form of screw-division permits, by a simple manipulation of the 

 swing-piece of the handle K, the knife to approximate directly to the 

 upper plane of the object to be cut. The automatic raicrometnc for- 

 ward movement can then be immediately begun. 



