698 PHARMACEUTICAL BOTANY 
harden. Now trim the paraffine block with a sharp scalpel so 
that the faces form right angles with each other. Adjust the 
wood in the clamp of the microtome and the microtome blade 
so that the top of the paraffine block just touches the near surface 
of the microtome knife. Make certain that the knife edge and 
the two opposite faces of the paraffine block are perfectly parallel. 
Now trim the remaining two sides of the block close to the object. 
Adjust the automatic feed of the rotary microtome by moving 
dial to number on scale representing thickness in microns desired 
of sections and turn wheel of microtome. It will be observed that 
the carrier moves up and down and with each downward move- 
ment slightly forward, causing the knife to cut sections which 
adhere in ribbons. 
Transfer the ribbons by means of a camel’s hair pencil or 
dissecting needle to a piece of dust free paper with the side down- 
ward which was next to the knife. The ribbons are now ready 
to be mounted on slides. 
The slides to be used should only be those which are devoid of 
grease or dirt of any kind particularly on the surface upon which 
the ribbons are to be mounted. A very good plan is to keep a 
number of slides intended for this purpose submerged in a 
saturated solution of potassium dichromate in concentrated 
sulfuric acid. ‘These can be taken out as needed and thoroughly 
rinsed with water. 
With a clean cloth stretched over the forefinger vigorously rub 
one surface of each slide until perfectly dry and free of lint. Then 
place a small drop of Mayer’s albumin fixative on clean surface 
and rub over the surface. (The formula for Mayers Albumin 
Fixatiwe is as follows: Egg white and Glycerin, equal parts, 
Salicylate of Soda, 1 Gm. to each 100 cc. Mix thoroughly and 
- filter.) Now flood the surface with water and cut the ribbons 
into segments of the desired length and arrange in rows on slide, 
being careful to have the segments somewhat shorter than the 
length of the cover slip because of tendency of paraffine to stretch 
when warmed. Warm slide gently by holding high above a 
bunsen flame or flame of an alcohol lamp until ribbons stretch 
out in smooth fashion. Absorb superfluous water, from beneath 
ribbons with blotting paper held to their edges and at same time 
