732 Answers to Queries. 
brush. The strong acid must on no account be allowed to come 
in contact with the skin, as it is very likely to cause painful sores. 
For process No. 2 you require powdered fluor spar and sulphu- 
ric acid, also a leaden dish of the proper size and shape, to 
correspond with the article requiring to be etched. In the dish, 
place the fluor spar, and across it arrange small lead strips to 
support the article. All being ready, pour in the sulphuric acid 
so as to well cover the fluor spar ; place the whole in a warm place 
(but not hot enough to make the wax soft) for a short time, and 
when the glass is etched deeply enough remove the wax with warm 
turpentine on flannel. In some cases, it is possible to dispense 
with the lead dish by applying the mixture of spar and sulphuric 
acid directly to the article. 
It is also possible to write words on glass by mixing hydro- 
fluoric acid with gum, so as to be able to write with a quill pen, 
and then after some hours wash off the gum with water. The 
sand-blast requires special machinery, whereby a jet of sand is 
powerfully projected on to the article which has been previously 
coated with paper lace, or any like substance, over those parts not 
intended to be etched. J, WG 
352.—Olfactory Mucous Membrane.—In order to get a good 
idea of the olfactory region, it would be advisable to make 
preparations both of the olfactory epithelium, and also of the 
entire nasal region. 
The true olfactory cells ina Frog or Newt may be demonstrated 
by the simple method of slitting up the nostrils with scissors, and 
subjecting the entire head to the action of dilute alcohol for, say, 
24 hours, then staining the still entire head in picro-carmine, and 
teasing out some of the epithelium from the olfactory region in a 
drop of glycerine. 
Good preparations of the olfactory epithelium of Mammals 
may be obtained in the following way :—Procure the head of a 
Sreshly-killed Sheep, Rabbit, or other animal, and divide it, in its 
long axis, with a sharp saw, parallel to the nasalseptum. Cut out 
the nasal septum so as to expose the olfactory region, the brown 
colour of which renders it easily recognisable. Harden this in 
Miller’s fluid for two days, and then transfer to Chromic Acid and 
Spirit mixture for a week, and complete the hardening in weak, 
and then in strong, spirit. Vertical sections may be stained in 
logwood, or double-stained with logwood and picro-carmine, and 
mounted in dammar or Farrant. 
Tranverse sections of the whole nasal chamber are highly 
instructive, as showing the relations of the various structures to 
one another. ‘The head of an animal, such as Rabbit, should be 
injected from the aorta with carmine or Prussian blue, and after 
this operation the skull should be opened, and the brain carefully 
