DOUBLE STAINING WITH H#MATOXYLIN AND ANILINE, 875 
cerned, be carried on indefinitely. It was used on this occa- 
sion for the purposes of demonstration to others, while the 
whole attention could thus be directed to the specimen, a 
casual glance being cast at the pieces of paraffin from time 
to time. As far as possible draughts of air should be 
avoided, as they tend both to cool the stage and blow the 
flame, so that the temperature may rise rapidly to an unde- 
sirable degree. 
To prevent evaporation of the fluid under observation it 
is usual to smear the edges of the cover-glass on which the 
specimen is placed, and which should be rather smaller than 
that lying on the copper disc, with oil, but cacao butter may 
for this claim the preference. The second cover-glass, on 
the under surface of which is smeared the blood to be ex- 
amined, is touched round its edge with solid cacao butter. 
It is now lightly dropped upon the glass that has been 
already raised to the required temperature on the stage. 
The solid cacao butter prevents the first shock, by its pro- 
jection from the under surface of the glass, and the conse- 
quent scattering of the fluid and the formation of air-bubbles 
are prevented, while the moment that it melts it runs 
evenly and uniformly round, hermetically closing the space 
between the two glasses. 
If the instrument be well warmed before being fixed to the 
stage of the microscope it will be more quickly put into 
action; and in cold weather especially it is advisable to do 
so, as the temperature of the surrounding air makes a marked 
difference in the time required for raising the stage to the 
required heat. 
The woodcut represents the hole in the disc as square, but 
it is more easily made circular, and perhaps more effective, as 
the heat can then approach the centre of the glass cover, 
where the specimen lies, equally from all directions. 
A DovusLeE STAINING with H@MATOXYLIN and ANILINE. 
By W. H. Pooxz, B.A. Oxford, Science Master at 
Friars’ School, Bangor. 
WueEN engaged last autumn in the Anatomical Depart- 
ment of the Oxford University Museum in making micro- 
scopic preparations of brain, my attention was especially 
directed to the staining of the sections. 
My first attempts were made with hematoxylin and care 
