CARBOLIC ACID IN MOUNTING, T7 
found doubled beneath them, as in all other methods of killing 
with which we are acquainted. 
The acid used for this purpose, or for mounting, should be the 
strongest solution,—having just enough water in it to keep it fluid 
at ordinary temperatures. To use it for mounting it is only 
necessary to drop the specimen into the acid, and in a few mo- 
ments transfer it to the prepared cell containing the medium in 
which it is to be mounted. Suppose it is desired to mount a 
mosquito, or a plant-louse, or any minute insect which requires no 
preliminary treatment, drop the insect into the acid, and in a few 
minutes it will be seen that the fluid has thoroughly penetrated 
the body. Then it is quite immaterial whether the specimen is to 
be mounted in water, or glycerine, or balsam, for carbolic acid will 
mix as readily with one as with the other. Fill the cell with the 
medium to be used; place the specimen on a clean slide, and 
take up the excess of fluid with blotting paper ; then transfer it to 
the cell and arrange the parts with needles, when the cover-glass 
can be applied. 
When deep cells are required for balsam mounts we are accus- 
tomed to using brass curtain-rings, cemented to the slide with 
shellac, or with hard balsam. Shellac is preferable if asphalt 
varnish is to be used to finish the mounts. After the cover is 
applied the slide may be gently heated until the outside balsam is 
hard enough to keep the cover in place. Then the excess of 
balsam can be cleaned off, and a ring of shellac applied to protect 
the balsam, when the brass ring may be concealed by any finish- 
ing varnish. The same cells may be used for glycerine or water 
mounts. 
Another way to make deep cells for balsam is as follows :— 
Build up a cell of adequate depth for the object, by successive 
layers of benzole-balsam, and let this harden thoroughly. Then 
fill it with soft balsam, and mount as before. As a precaution 
against injury to the cell three pieces of thin glass may be placed 
within it to support the cover. Such a cell can be finished with 
damar varnish, and makes a very attractive mount. 
When insects require any preliminary treatment to make them 
transparent, the soda solution should be thoroughly removed by 
washing with water, after which the specimens should be taken 
out one by one, the superflous water removed with blotting paper, 
and then thrown into the carbolic acid. 
This method of mounting is the simplest and best one we know 
of. If the reader chooses to experiment with it let him take the 
head and proboscis of a blow-fly, or any part of an insect that may 
be available, and, without any preliminary treatment, place it in 
carbolic acid, and mount it in balsam without pressure. A single 
trial of this kind will convince him of the ease with which excellent 
