26 THE AMERICAN MONTHLY [Feb 
cheaper. As a great number of stains are to be made, it 
is economy to have scales and buy the materials at low 
prices. But little other apparatus is needed. 
Directions are given for procuring eyes from living sub- 
jects or those just dead, as changes take place almost im- 
mediately after death. Hardening must be done at once. 
But as many advantages are lost by hardening, the study 
of fresh specimens is also recommended. Hardening 
shrinks and packs the cells close together. But fresh 
tissues require certain preparations. ; 
The various liquid exudations are taken up on a plati- 
num loop, transferred to slides, covered and examined 
for cholestearin crystals, fatty degenerate cells, etc. which 
hardening solutions would dissolve. These cover-glass 
preparations are often stained, washed, dried and perma- 
nently mounted in Canada balsam. Cover-glass prepara- 
tions are also made from soft tissues such as gliomata. 
Firmer tissues, like sarcomata of the chorioid, require 
teasing in liquid by needles; or if still firmer first soak 
them 24 hours in alcohol, or Muller’s fluid. 
The author describes at length, eleven methods of har- 
dening, as follows: In alcohol, Muller’s fluid, Erlitzki’s 
fluid, corrosive sublimate, picric acid, picric acid subli- 
mate, formalin, osmic acid, nitric acid, platinum chloride, 
Herman’s solution. The advantages and disadvantages 
of each method are known. Erlitzki’s fluid consists of 50 
bicromate of potash, 10 sulphate of copper to 1000 of dis- 
tilled water, works. quicker than Muller’s but produces 
shrinkage. Formalin was first used in micro work by 
Blum. It must be remembered that formalin undergoes 
chemical changes when exposed to light and air. Use it 
in the dark. The same is true of osmic acid which is 
very volatile. It brings out the karyomitotic figures and 
renders fat globules very dark. Hermann’s solution is a 
mixture of 15 solution of platinum chloride (1 per cent), 
4 solution of osmic acid (2 per cent), 1 glacial acetic. It 
