CHAPTER II 
REAGENTS 
No really new reagents have come into general use since the 
third edition of this book was published in 1915, but there have been 
valuable modifications of some of the older formulas, and improve¬ 
ments in the use of time-honored combinations. The following 
account includes those which are used constantly and also a few 
which are used occasionally. The MicrotomisVs Vade-Mecum, by 
Lee, is written from the standpoint of the zoologist, but it contains 
very complete formulas for stains and other reagents, which are just 
as useful to the botanist. 
A list of reagents, with the quantities used by the average student 
in a three months’ course in methods, is given in chapter xxix. 
“Stains and Staining” are described in chapter iii. 
KILLING AND FIXING AGENTS 
Usually the same reagent is used for both killing and fixing. 
The purpose of a killing agent is to bring the life-processes to a sud¬ 
den termination, while a fixing agent is used to fix the cells and their 
contents in as nearly the living condition as possible. The fixing 
consists in so hardening the material that the various elements may 
retain their natural condition during all the processes which are to 
follow. Zoologists often use chloroform or ether for killing an 
organism, and then use various fixing agents for various tissues. 
No promptings of humanity restrain the botanist from the vivisection 
of plants, but separate reagents for killing and fixing are sometimes 
used, e.g., material may be killed by placing it for a short time in 
Flemming’s fluid, which is a very rapid killing agent, after which the 
fixing may be completed in a chromo-acetic solution, without any 
osmic acid, thus securing the advantages of a very rapid killing 
without the blackening which results from a prolonged treatment 
with a solution containing osmic acid. 
Probably no process in microtechnic is in more urgent need of 
improvement than this first step of killing and fixing. Nearly all 
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