1890.] Microscopy. 857 
method. All who have had the opportunity of examining specimens 
prepared by Lo Bianco can appreciate readily the great advantages 
which may result from the careful application of his methods, and can 
perceive how greatly we are indebted to him and to Professor Dohrn 
for their publication. 
Alcohol is, of course, ae as preservative fluid, but certain 
precautions are necessary in its u Except ina very few cases it 
is unnecessary to use it in its fall strength, 70% being quite suffi- 
cient for preservation, and producing much less contraction and 
fragility in delicate organisms. Strong alcohol should be reduced with 
distilled water to the desired strength, ordinary spring water frequently 
containing a sufficient amount of carbonate of lime and other sub- 
stances in solution to give a cloudy precipitate, after a time, which 
may effectually destroy the appearance of a specimen. Furthermore, 
delicate organisms should first be placed in weak alcohol (35 to 50%) 
for from 2 to 6 hours, the changing of the fluids being effected by a 
siphon, a small quantity of the weak alcohol being withdrawn and 
stronger added, until finally the desired strength is obtained. Wit 
delicate and gelatinous structures the increase in the strength of the 
alcohol should be as gradual as possible. 
In many cases it is necessary to wse a hardening or fixing reagent: 
before the final consignment to alcohol, which is principally useful as 
a preservative. The most useful fixing reagents, according to Lo 
Bianco, are the following: 
Chromic Acid. —ı per cent. in fresh water. Objects should not 
remain in this fluid longer than is necessary to fix them, as they are 
apt to become brittle. Subsequently they should be well washed with 
distilled water to prevent the formation of a precipitate when placed 
in alcohol, and also to prevent their taking on too green a tinge from 
the reduction of the acid. 
Acetic Acid, concentrated, kills rapidly contractile animals, but 
must be used with caution, as it produces a softening of the tissues if 
they are subjected for too long a time to its action. 
Osmic Acid.—1 per cent. solution, hardens gelatinous forms well, and 
preserves their transparency, but its prolonged action renders the 
object brittle and gives it a dark brown tint. Objects hardened in 
it should be well washed in distilled water before being placed in 
alcohol. 
Lactic Acid,—1 part to 1000 parts sea-water fixes larvae and gelatin- 
ous forms well. 
