1896. ] A Simple Freezing Device. 199 
sition of the two pails should be reversed. The person using 
the microtome does not need to rise from his chair to accom- 
plish this, since he can easily reach the pail nearest him and 
raise or lower it as necessity requires. The weight to be lifted 
is simply the weight of the brine, since the weights of the two 
pails with their content of ice and salt balance each other. 
The shifting of the pails therefore occupies only the left hand, 
leaving the right free. The falling of the lower pail indicates 
that most of the brine has run through. If a more accurate 
indication is needed one may insert in one of the rubber tubes 
aglass [-tube with a cork at the top of the free arm of the 
tube. A black feather may be fixed to the cork in such a 
way that the end dips in the current and shows by its deflec- 
tion the direction and force of the flow. When too much 
brine has accumulated the tem perature rises and freezing pro- 
ceeds too slowly; a part must then be siphoned off. Usually 
this happens once, or at most twice, during the course of one 
day's use of the apparatus. The addition of more ice is very 
seldom necessary. 
Closed. Objects already frozen will remain so under these 
‘onditions as long as the brine continues to flow. If the ap- 
Paratus is to be left for a longer time the brine should all be 
‘awn off and thrown away, and the faucets closed. A mo- 
ment's flow will render the apparatus ready for use again. — 
During a year’s test in cutting both plant and animal tis- 
“v<s this apparatus has proven entirely satisfactory. Its prin- 
= advantages are as follows: 
“onsistency, 
“ara danger of over-freezing, which has proved “ —— 
On th in the carbonic-acid-gas method, is entirely obvia . 
is of © other hand, no difficulty is experienced in freezing, 
ten the case with the ether method. 
Oey can be applied to any microtome which has at 
ho ne ovement of knife or object carrier. In mos i 
previous embedding is necessary but fresh material, or tha 
reserved in aqueous media, may be placed in a syrupy 
