578 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
parations and others in formalin. The combination of formalin with 
other hardening reagents has not as yet apparently received much 
attention. Dr. Fish thinks that its use in this connection will un- 
doubtedly be of great value in macroscopic as well as microscopic 
methods. Good results may be obtained with nerve-tissues when the 
following mixture is employed : — Water, 2000 ccm. ; formalin, 50 ccm. ; 
sodium chloride, 100 grm. ; zinc chloride, 15 grm. The specific gravity 
should be about 1*05; in practice the specimen is left in this mixture 
for a week or ten days — it may then be transferred to a mixture of water 
2000 ccm. and formalin 50 ccm., and it may remain in this solution in- 
definitely, if the jar be kept tightly covered. To prevent the freezing of 
formalin solution, it is suggested that alcohol might be mixed with it, 
say equal parts of 95 per cent, alcohol and 2^ per cent, formalin. 
Material treated in the way described has yielded most satisfactory 
results histologically. Formalin may replace osmic acid in the Golgi- 
Oajal method. A mixture which was used with very great success was 
the following: — Muller’s fluid, 100 ccm. ; formalin 10 per cent., 2 ccm. ; 
osmic acid 1 per cent., 2 ccm. 
Method of Preserving Nervous Tissue.* — Dr. G. E. Elliott has 
some notes on the various methods of preserving nervous tissue. They 
seem on the whole to be addressed to the beginner, but there are one or 
two points of special interest. He recommends Muller’s fluid, when it 
is especially desired to prevent shrinkage of the specimen, to trace nerve 
tracks, or , when cheapness is a matter of importance. The time necessary 
to harden is considerably reduced by using the fluid hot, say at 75°. 
Formalin is looked upon as, perhaps, the most valuable method for 
preserving tissues which we possess. If, says Dr. Elliott, you once 
prepare your specimen in this, and forget to change it for three months, 
you will probably find it preserved all right. The best method for 
making dry specimens of the brain appears to be that of Giacomini. 
Among the staining methods to which he refers, he finds that one of 
the very best of the more recent stains is that of Nissl. Small pieces 
of fresh tissue arc placed at once in absolute alcohol and left from two 
to six days. After imbedding in celloidin or in paraffin, the specimen 
is best stained by placing the sections in a watch-glass which can be 
heated over a flame to a temperature of 7 0°. The author has succeeded 
in getting excellent results by allowing the sections to remain over- 
night in a 25 per cent, solution of methyl-blue. This gave beautiful 
staining results of cell-processes together with nerve-fibres. The cells 
are apt to be overstained unless a very weak solution is used. As may 
be supposed, the Golgi stain is recommended for studying cell structure, 
as it brings out magnificently the processes of the cell. A neuroglia 
stain which can be recommended, is one modified by Dr. Mallory of 
Boston, from one of Weigert’s ; by this method, small bits of tissue are 
kept from four to seven days in a solution of formalin 10 c.c. and 90 c.c. 
of a saturated solution of picric acid ; transfer to a 2 per cent, solution of 
bichromate of ammonia, and leave from one to two weeks, wash in water, 
and place in alcohol for 24 hours. Mount in celloidin, and stain lightly 
with carmine ; the sections are now to be further stained thus : — Anilin- 
gentian for from 5 to 20 minutes, decolorise in a solution of one part 
* ‘ The Post Graduate/ xi. (1896) pp. 336-48. 
