SCIENTIFIC SUMMARY. 
213 
mony into Sb 2 0 4 ) calculated the proportions of the metals from the increase 
in weight. This method, although by no means giving him accurate re- 
sults, served very well for rough approximate determinations. He cites it 
simply as an easy and convenient process for obtaining a close idea of the 
constitution of any alloy composed of the two metals. Possibly the method 
might be so modified as to give accurate determinations. 
MICROSCOPY. 
The Inhabitants of the Mouth and Teeth . — Under this somewhat uninviting 
title a paper has lately been written by Herr Schrott, and has been trans- 
lated in the Americau Dental Cosmos by Herr A. Petermann of Munich. 
We cannot abstract all the writer says, but the following account of the 
Spirilke is not without interest. Spirillse are a variety of the vibriones. 
They are found in hollow teeth in which the saliva does not change daily. 
Very often some, with one or two windings, are found between the 
teeth and under artificial sets. No microscopical object stimidates the 
admiration of the spectator more than these little lines in the form of a 
screw, and which move, like living corkscrews, with immense rapidity, for- 
ward and backward, without it being possible for the eye or the mind to 
conceive in what manner these relations are effected. To have a very good 
view, it is necessary to cut out a little piece of damp caries from a newly- 
extracted tooth ; put this in one or two ounces of distilled water, cover the 
vessel in such a way that the air has a little entrance, and keep these in- 
fusorise two or three weeks in this manner. After this time, if you take the 
caries out of the glass and put an adherent drop of water under the micro- 
scope, yon will observe an immense quantity of spirillae, which obtain from 
one to six windings. 
A good Preservative for mounting Animal Tissue . — In a recent number of 
Brown- Sequard's Archives of Physiology it is said that carbazotic acid is a 
capital mounting substance. This acid is only moderately soluble in 
water, and a saturated solution may therefore be employed. It possesses the 
further advantage of being very cheap. It is admirably adapted for all 
tissues containing much blood, and therefore for specimens of liver, lung, 
&c. It appears to act by effecting coagulation of the albuminous substances, 
though, unlike alcohol and chromic acid, it does not occasion any fusion of 
the constituents of the tissue. The red globules retain their form and cha- 
racters extremely well. The portion of tissue required to be examined 
should be plunged into the solution, and after the lapse of twenty-four 
hours it will be found to have acquired sufficient firmness to permit of very 
fine sections being made with a razor. The saving of time by this method, 
as compared with the chromic acid, is immense. The preparations will take 
colour from carminate of ammonia, and may be preserved in glycerin. 
Cheap and good Immersion Objectives . — The Monthly Microscopical Journal, 
quoting Max Schultze, states that a German optician, Gundlach of Berlin, 
has succeeded in making better and cheaper object-glasses than even Nachet 
or Hartnack. He sells an immersion --inch at as low a price as 21. 12s. In 
this country Mr. Crouch is in advance of the English makers in offering an 
