161 
or otherwise, and thoroughly washed until all alkali is 
removed. It can then be transferred to alcohol or glycerine 
for preservation, if it is not intended to mount it for the 
microscope immediately. But if it is to be put up perma- 
nently, I find nothing answer as well as the material known 
as Glycerine-Gelatine, and which I have been in the habit of 
making after a formula of my own, and supplying to the 
dealers in microscopic materials for some time past. This 
medium is much more readily used than Canada Balsam, is 
cleaner to manipulate, requires no alcohol or turpentine to 
clean off of the slide, and shows the structure of the odonto- 
phore in a manner which nothing else that I have tried will. 
It is also a capital material for nearly every kind of animal 
and vegetable tissues, and in fact I consider it one of the 
most valuable media which the practical microscopist pos- 
sesses. Its mode of use I have more particularly described 
in a paper lately read before the American’ Microscopical 
Society, and which will be shortly published in one of the 
English Journals, to which I must ther efore refer for further 
particulars. 
Pror. A. M. Epwarps exhibited at tne same time a series 
of specimens illustrating the above paper, and showed them 
by means of what he has called his Demonstrating Microscope. 
This is a form of instrument which he devised for use in 
his lecture room, where it.was desirable to pass around and 
exhibit in a satisfactory manner, and to a class of students 
several microscopic objects in succession. It consist8 essen- 
tially of a microscope of the ordinary form, supported upon 
uprights and a tripod base. In this form it may be used in 
the laboratory and upon the table, but when used in the 
class-room, by means of a simple contrivance it can be 
unshipped from its upright supports, and can then be held in 
the left hand by the student, whilst the rightis used to 
manipulate the adjustments. But so that proper illumina- 
tion. of the object under examination may be secured, the 
mirror, which is upon a tubular arm, and which can be 
swung from side to side so as to obtain oblique illumination, 
