2SI 
SUMMARY OP CURRENT RESEARCHES RELATING TO 
microtome screw is 0*5 mm., and as there are 100 teeth on the edge of 
the plate, one turn equals 0 * 005 mm. If a section-thickness of 0 • 03 mm. 
be desired, the screw l is undone, and the circle segment c pushed 
hack until the mark 3 corresponds with that on the vernier, after 
which it is tightened up. The handle a is then pushed from the upright 
b to the upright d. By this action the catch m pushes the micrometer 
plate round, and the object-holder is thereby raised 0*03 mm. The 
handle is then pushed back again to b and the section made. 
If the preparation has been raised too high, the object-holder is 
lowered in the following manner : — The screw e is unloosed by means 
of the rod /, and then the handle o is pushed in the direction of the 
arrow. This action sets free the catch m, so that the preparation-holder 
is easily lowered by screwing down the micrometer plate, and then pushing 
down the preparation-holder until its lowest part is in contact wdth 
