4 °7 
necessary to dehydrate by passing through successive 
strengths of alcohol, as the shrinkage would be great 
if the tissue were passed direct from water to absolute 
alcohol. This may be effected in the following way :— 
To 9 c.c. of water containing the washed tissue add 
i c.c. of absolute alcohol. The strength of alcohol 
is now ten per cent. Leave for ten minutes. Take 
out 5 c.c. and add I c.c. of alcohol, the strength is now 
twenty-five per cent. Leave for ten minutes. Take 
out 2 c.c. and replace by I c.c. of alcohol; the strength 
is now forty per cent. Leave for ten minutes. 
Continue in this way to take out 2 c.c. and replace by 
i c.c. of absolute alcohol. It will be seen that the 
process takes an hour. If the tissue is not going to be 
imbedded stop at eighty-five per cent. Otherwise at 
this stage place in absolute alcohol ready for passing 
through cedar wood oil. 
N.B.—This process is only necessary where extreme care is to be 
taken in the preservation of histological details, otherwise change 
from the water to (about) eighty-five per cent, alcohol directly and 
renew it once. 
Table for Passing through Increasing Strengths 
of Alcohol 
9 c.c. H 2 0 + i c.c. ioo% alcohol .= io % alcohol. 
5 c.c. io % + i c.c. „ „ - 25 „ 
4 c.c, 25 + 1 c.c. „ „ = 40 
3 c.c. 40 4- 1 c.c. „ „ =55 
2 c.c. 55 + 1 c.c. „ „ = 70 
1 c.c. jo 4~ i c.c. ,, ,, = 83 ,, 
Any convenient multiple of these quantities may, 
of course, be used. 
Stains, etc. 
1. Romanowsky Stains.—Vide p. 21. The best 
stain for parasites in the blood, etc. 
