90 
On Methods of 
E Monthly Microscopical 
Journal, Aiig. 1, 1869. 
through, the necessary communication is to be established with the 
caoutchouc tubes, and the pinch-cocks opened. Those, however, 
who work more frequently with gases will not be satisfied with a 
provisional chamber so easily destroyed. Then it is better perma- 
nently and firmly to cement the conducting glass tubes into grooves 
in the glass slide. The space, which is to be filled with gas, can 
then be again enclosed by a wall of putty. 
A slide, which is used for such examinations with gas, must be 
held down upon the stage of the microscope, because the conducting 
gas tube drags on it, in consequence of which the object may be 
moved out of its position during the examination. The gases 
should be evolved from wash-bottles which are fixed upon the table, 
so that definite relations may subsist between the wash-bottles and 
the microscope, whatever may be done with the gas apparatus 
placed at a distance from the table. That I may be quite indepen- 
dent in my microscopic labours of the aid of assistance, and in order 
that table and hands may not be taken up with other than purely 
microscopic objects, I arrange my gas apparatus below the table in 
such a way that by movements of the feet I am enabled to set the 
one or the other agoing. If carbonic acid, for example, is to be 
made use of, I place the apparatus below my table in such a way 
that a bottle holding the hydrochloric acid can be raised from the 
floor by means of a foot-board and a cord running over puUies, and 
the acid thus caused to run into the evolution-bottle by a caout- 
chouc tube passing between necks in the lower parts of the bottles. 
From the evolution-bottle a caoutchouc tube leads then into the fixed 
wash-bottle on the table, and from this proceeds the communication 
with the microscope. The conduction of carbonic acid to a micro- 
scope requires, however, the possibility of its exchange for atmo- 
spheric air. I insert, therefore, a T-shaped tube between the 
wash-bottle and the glass slide. The direct arm of this tube lies 
in the line of communication between the wash-bottle and the glass 
slide, with the cross-piece turned towards the observer. To this is 
now attached a long caoutchouc tube, the extremity of which the 
observer holds between his teeth. Between the T-shaped tube and 
the wash-bottle a clamp is applied. If I now open the clamp, lift 
the bottle containing the acid by treading down upon the foot-board, 
send in this way carbonic acid into the wash-bottle, compress at 
the same time the caoutchouc tube between the teeth, the gas must 
pass over the shde. But if I close the clamp, and suck at the end 
of the tube in my mouth, I draw atmospheric air into the chamber 
from its opposite side. Thus it is in one's power to introduce a 
succession of atmospheric air and carbonic acid whilst observation 
is being carried on, and the hands are left free for necessary mani- 
pulations. A second, so-called Deville's apparatus, under my table 
arranged in the same manner as the first, is suitable for the evolu- 
