418 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
last few years in the laboratory, hoping to so shorten and modify existing 
methods that every step may be taken by the student himself without too 
great an expenditure of time. The following are the results, and they are 
given, not because they are the best possible methods that might be used 
if unlimited time were at the disposal of the student, but as methods 
that give excellent results in a very short time. 
Picric Alcoholic Method . — The hardening and fixing solution consists 
of 95 per cent, ethyl alcohol, 250 ccm. ; water, 250 ccm. ; picric acid 
crystals, 1 gram. 
The tissue is cut into pieces of moderate size and placed in a 
preserving jar containing about 25 to 50 times as much of the preserva- 
tive as there is tissue. It is well also to suspend the tissue or support it 
on absorbent cotton, or to stir the tissue around occasionally. The 
tissue should be left in the picric alcohol about 24 hours. If the piece 
is small, 12 hours will do, and an immersion of 2 to 3 days seems to do 
no harm. After one day the tissue is placed for 24 hours in 67 to 70 
per cent, alcohol, and then for one day or longer in alcohol of from 75 
to 82 per cent. It may be left indefinitely in this. Finally, just before 
imbedding, the tissue is dehydrated one day only in 95 per cent, or 
stronger alcohol. It may then be infiltrated with paraffin or collodion 
in the usual manner, the whole time required being 7 days, at the 
longest, to harden, infiltrate, and imbed a tissue ready for sectioning. 
The picric-alcohol method has given excellent results for all tissues 
except peripheral nerves. It is especially to be recommended for organs 
or parts possessing ciliated epithelium. 
The double stain of haematoxylin and picric acid gives very sharply 
defined appearances, the haematoxylin staining the nucleus and the picric 
acid the cell-body and also the ground-substance somewhat. 
If ammonia-carmine is used as a stain, more sharply differentiated 
appearances are obtained by dehydrating with the following: — 95 per 
cent, alcohol, 100 ccm. ; glacial acetic acid, 1 ccm. ; picric acid crystals, 
1/10 gram. 
Nothing has been found more satisfactory for a clearing medium 
than: — Carbolic acid crystals (melted), 40 ccm.; turpentine (oleum 
terebinthinae), 60 ccm. 
And for a mounting medium, Canada balsam, dissolved to the con- 
sistency of thick syrup in xylol or cedar-wood oil, has given excellent 
results. 
Flemming's Chrom- Acetic Acid Method . — This has proved satisfactory 
for the rapid fixing of peripheral nerves and for stratified epithelia. 
For the stomach and intestines it has not proved so satisfactory as the 
picric alcohol. Chromic acid crystals, 6 grams. ; glacial acetic acid, 
2 * 4 ccm. ; water, 2400 ccm. 
The tissue is cut into pieces of moderate size and ^placed in 50 to 75 
times its volume of the fixing agent for 12 to 24 hours. It is then 
washed two hours or more in water and left about 12 hours in 50 per 
cent, alcohol, then placed indefinitely in 75 to 82 per cent, alcohol. It 
may be dehydrated, infiltrated, and imbedded as described for the picric- 
alcohol method. 
Haematoxylin is, on the whole, the most satisfactory stain, but the 
staining is not so satisfactory as after the use of picric alcohol. The 
