OF MICROSCOPIC OBJECTS. 128 
plamts that this mixture becomes turbid with keepiné; but 
I think this must only be the case when some impurity has 
got into the bottle. 
Carzporic Actp.*—The addition of a few drops of this to 
distilled water prevents the growth of interfering substances 
which would take place if pure water alone were used, and 
is therefore valuable as a preservative fluid. The same 
solution also is convenient, as it instantly kills infusoria, and 
almost everything that has life; and, indeed, is useful in 
the student’s gathering-bottles for the same reason. It is 
very highly spoken of as forming one of the constituents in 
the following formula for use in mounting soft animal 
textures :— 
Argenious acid, 20 parts. 
Crystallized carbolic acid, 10 parts. 
Alcohol, 300 parts. 
Distilled water, 700 parts. 
The Rev. W. W. Spicer, in his translation of Johann 
Nave’s work on Algz, recommends the following fluid for 
their preservation :—Pure alcohol, 3 parts; distilled water, 
2 parts; glycerine, 1 part. If the desmid or other alga 
be placed in this fluid in a cell, and not covered by a glass 
for a time, the water and alcohol will evaporate slowly, and 
the mixture will become more dense in proportion, but quite 
gradually, and therefore without any destructive influence 
on the object. During this operation, water is withdrawn 
from the frustule, and the glycerine, which is not volatile, 
takes its place without causing any distortion of the object. 
Castor Om.—This is a very useful preservative for 
crystals and other objects. Many salts are quite destroyed 
when Canada balsam is used with them; but very few are 
acted upon by this oil. To use it, it must be dropped in 
sufficient quantity to cover the crystal or object to be 
* Dr. Crace Calvert stated at a meeting of the British Association, 
that after careful experiments he finds carbolic acid “ prevents the 
development of protoplasmic and fungoid life.” 
