ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
663 
of the knife is very restricted, the full extent of the slide-way cannot be 
utilized. In most cases this small displacement is not sufficient, so that 
it is necessary to dismount the object during the work and readjust it. 
This entails loss of sections, irrespective of the inconvenience of such a 
process. 
To get rid of this difficulty, Herr R. Jung of Heidelberg has, under 
the author’s direction, constructed an object-carrier with vertical dis- 
placement. In one of these, represented in fig. 72, the frame O, 
Fig. 72. 
carrying the object-clamp, is movable in the vertical direction. This 
runs in a prismatic groove with so much friction that no fixing- 
arrangement is necessary to keep it in any given position. The 
Fig. 73. 
St 
movement is effected by rack and pinion. The frame rests upon a 
steel base b, provided with a ratchet in which works a toothed wheel, 
set in motion by the lever r. One turn of the lever effects a rise of 
the frame, and consequently of the slide-way, of 1*2 cm. 
To begin work, the lowest position is given to the frame carrying 
the object-clamp, the paraffin block is mounted somewhat high, and the 
