ZOOLOGrY AND BOTANY, MICROSCOPY, ETC. 
451 
The guillotine A moves up and down two perfectly straight steel 
bars a, a , which act as slides and are kept rigid by gays b, b, b, b, each 
controllable by a special nut b\ b', b' . To render the movement more 
exact or delicate, the guillotine is provided with two rollers c, c , mounted 
on a strong steel spring d, which exerts a sufficiently strong pressure on 
the steel bars. The regular movement of the guillotine is, moreover, 
secured by making the handle pass through a hole / on a higher level 
than the sliding-holes h h of the guillotine. 
The razor B (fig. 117) is formed by a blade of fine steel with two 
cutting edges i, i ; it is thick, scarcely flexible, aud is provided with two 
Fig. 117. 
cars or trunnions for fixing to the guillotine. Fixing is attained by 
slipping the razor into two oblique notches kJc. Immobility and 
obliquity are accomplished by manoeuvring four screw-bolts, placed two 
and two on the body of the guillotine Z, Z, Z, Z. 
The horizontal carrier C bears two lateral notches which engage in 
two long and solid horizontal slides m, on which certain graduations 
allow the determination in advance of the precise width desired for the 
paraffin blocks, so as to produce ribbons of required length, and of the 
required number of sections for the said length. 
The precision screw D, moved by a crank 0, displaces horizontally 
the carrier with the paraffin block. This screw has a thread interval of 
about half a millimetre, and is kept exactly in its place, without un- 
steadiness, by a screw p, whose hollowed-out end receives the end of the 
precision screw. 
The horizontal carrier C is surmounted by a supporting piece E, 
intended to receive the ordinary block-bearers p formed of a disc fitted 
with a metallic stem, on which the paraffia blocks have been previously 
soldered. A hole bored in E receives the butt of the block-bearer, 
steadied by a small bolt ; neither hole nor bolt is visible in the figure. 
Around the base of E is a graduated dial E, regularly notched for 
receiving the catch of a special spring q. By means of these graduations, 
notches, and spring, the paraffin blocks can be accurately set at various 
angles, and cut geometrically to the desired form. The supporting 
piece and dial, really one, turn upon a pivot accurately centered in the 
carrier. A small index, not visible in the figure, reads off the dial 
graduations and section angles. 
The two razor-edges are 8*5 cm. long, and the total height of the 
instrument is 35 cm. 
In the orientation of series-sections on the slide, Prof. Eternod 
states that the best plan is to cut the paraffin blocks into accurately 
right-angled parallelopipeds, and afterwards slightly cut away the sharp 
