ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



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of a neck (fig. 68, o), a metal disc d, which is hollowed out (fig. 68, t) 

 for the reception of the imbedding plate (fig. 67, h). This plate consists 

 of a hard wood disc with shallow brass dowel, which fits pretty accurately 

 in the hollow of d (fig. 68, t), and can be firmly fastened thereon by the 

 screw m. On the imbedding plate the paraffin-block (fig. 67, p), which 

 has already received a parallelopipedal form from the adjustable im- 

 bedding frame, is erected with plane faces and firmly melted on. In the 

 iron base plate two steel pins (fig. 68, o and o"), equidistant from the 

 circumference and in two radii at right angles to one another, are in- 

 serted, their height exactly corresponding to the thickness of the neck 

 bearing the disc d. A conspicuous part of the apparatus is the guillo- 

 tine over the imbedding plate, worked by a vertical up-and-down push 

 motion. The hard brass plate s, by means of a long slit, grips the neck 

 of the disc d clamp-fashion, as well as one of the steel pins (o' or o"). 



Fig. 67. 



As the perpendicular distance between the flat top of the dome and the 

 underside of the neck o exactly corresponds to the thickness of the 

 plate 8, the latter can be worked to and fro as if in a slide-groove. 

 This movement is confined to the range between one of the steel pivots, 

 o' or o", and the central neck o. If the plate with the slit is drawn out, 

 it can then be lifted over the pivot and rotated round o, and placed over 

 the other pivot. This rotation is exactly 90°. 



The plate s carries, on two lateral projections, two vertical steel 

 columns c, whose bases are screwed into the plate. These columns sup- 

 port a crossbar n, the knife-carrier, by means of two collars so accurately 

 fitted that they only allow a clean vertical push of the knife-carrier. 

 The knife (fig. 67, M) is fastened on one face of the crossbar, and moves 

 with it. The down motion is by finger pressure ; the up by the resili- 

 ence of the two spiral springs f. 



When one face of the block has been cut, the knife-carrier is lifted 



