574 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
axis of the wheel r and runs on a steel tongue Z of the arm D The 
bMe^frame r B *° * “ a£sive arm M P r °J ec <™g from the left side’ of the 
. f“5 uated / ; ^ c “ of tte object-clamp is effected by means 
of the abutting edge N and the two pawls g and /. The pawl a is 
hinged to the upper end of the vertical arm of a bent lever, which turns 
about the axis of the wheel and has a horizontal arm projecting beyond 
Here the projecting arm carries a nickel block, which on raising the 
wheel strikes against the abutting edge N. The position of the latter 
can be adjusted in the piece F, which projects from the base-frame B 
and carries a division When by the action of the excentric the paral- 
lelogram and toothed-wheel are raised against the abutting edge, the 
pawl engages m the teeth of the wheel so that the latter is moved in the 
direction of the arrow, and the parallelogram and clamp connected with 
it are displaced towards the knife. At the beginning of the back move- 
Fig. 90. 
ment the pawl /prevents the wheel from turning back, while the pawl q 
is raised above the teeth owing to the nickel block of the lever resting 
on the cross-piece 0. The extent of the movement is determined by 
the adjustment of the abutting edge N in the piece F; each division of 
the scale corresponds to 2 • 5 /x. In order to render the movement as 
smooth as possible, a strong spring is brought between the base-frame 
and the arm D to counteract the weight of the upper part of the 
instrument. 
The new celloidin microtome is represented in figs. 90 and 91. Through 
a slit m the heavy cast-iron base-plate 6, a stand a , carrying the clamp 
or the preparation, can be inserted, and fixed in the desired position by 
means of the lever l. The preparation clamp is adjustable by two joints, 
and can be raised to the desired cutting plane by means of the rack L 
where it is fixed by the screw g. 
The arrangement for the movement and gradual lowering of the 
