184 MICROSCOPY. 
mal is killed, the head removed, the lower jaw disarticulated, and 
the two tympanic bulle exposed. One of these is opened and the 
cochlea, projecting into its cavity, removed and immersed in a half 
per cent. solution of chromic acid in water. The acid should be 
changed twice a week, and in about two weeks the soft tissues will 
be sufficiently hardened, and the bony parts may be softened 
enough for slicing with a razor. If not, one two-hundredth part 
of nitric or muriatic acid is to be added to the solution, and in 
from one day to three weeks, according to the hardness of the bone, 
the sections can be made. To support the internal parts while 
cutting, the cavity must be filled up. For this purpose inject the 
cavity with a hot solution of gelatine; or immerse it in a mixture 
of wax and cocoa butter melted together, and exhaust the air 
under a receiver of an air pump so that the melted wax can run 
in; or soak it, for an hour or two, in a thick solution of gum ara- 
bic contained in a paper bag, and then put the bag in absolute al- 
cohol for a day or two when the water will be sufficiently extracted 
to leave the gum in a tough state (methylated spirit may be substi- 
tuted for the absolute alcohol). The whole organ thus prepared is 
to be imbedded in the mixture of wax and cocoa butter,—or wax 
and sweet oil,—or lard one part, spermaceti two parts, and paraf- 
fine five parts, melted together over a water bath,—and sections 
cut with a very sharp razor. ‘The sections are to be floated off, 
stained with carmine, and mounted in glycerine or in acetate of 
potash (acetate of potash two ounces, hot water one ounce, dis- 
solve and cool; add spirits of camphor thirty drops, and filter) ; 
or transferred through water, absolute alcohol, and oil of cloves to 
dammar varnish or Canada balsam. 
PROBABLE Nature or THE Nerve Current.—Dr. L. S. Beale 
discusses this question in the “ Monthly Microscopical Journal,” 
and furnishes some very interesting speculations which are es- 
pecially valuable from tie author’s eminent familiarity with the 
subject. 
The, active part of the nerve fibre distributed to the peripheral 
organ’ which receives the impressions is described as consisting 
invariably of a pale, very transparent, faintly granular, but in the 
natural state perfectly invisible cord. Between this and the cen- 
tral origin, in man and the higher animals, intervenes a more OF 
; less. extended system of nerve cords through which impressions 
