Ig2 BACTERIOLOGICAL DIAGNOSIS. 
Where time permits it is a great advantage to rinse 
the section in distilled or clear rain water after re- 
moving it from the hematoxylin. 
The solution of hematoxylin is best bought ready 
made, as its preparation is somewhat difficult. Dela- 
field’s solution is about the best for general work. 
A counterstain is not really necessary for diagnostic 
purposes, and its omission hastens the process some- 
what. 
THE PARAFFIN PROCESS. 
Tissues which are to be cut in paraffin may be hard- 
ened in any of the fluids mentioned above. They are 
then dehydrated, cleared in chloroform or other fluid 
which mixes with alcohol and dissolves paraffin, and 
finally soaked in a mixture of hard and soft paraffin 
kept just at the melting point. This paraffin should 
be obtained specially for the purpose; the Cambridge 
paraffin is the best. It is made in two varieties, the 
soft, which melts at 48° C., and the hard, which melts 
at 55° C. The amounts of each which should be used 
for embedding depends upon the external temperature ; 
in very hot weather hard paraffin may be used alone, 
while under average circumstances a mixture of equal 
parts of each is best. 
We shall now proceed to describe the various pro- 
cesses seriatim. 
DEHYDRATION. 
This is very simple. The blocks of tissue are placed 
in weak spirit for a few hours or for a day, then 
