230 THE MICROSCOPICAL NEWS. 
producer, and which freezes 14 of an inch of tissue in 1% or 2 
minutes, using in the process about 2 drachms of ether, which cost 
something less than a farthing. ‘The instrument may be described 
under the heads of the Spray and the Microtome. 
The spray producer works on the same principle as the scent 
sprays which have been in use for a long time, where a jet of air 
playing across the top of a tube draws up the fluid from its interior 
by tending to make a vacuum in it. The bellows used are the 
ordinary hand ones sold for carbolic and other spray producers, 
these being as cheap and efficient as any that can be got. In 
working at the spray points, I began by selecting the size of air-hole 
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that these bellows could easily feed with a continuous blast of air, 
and then, experimenting with various sizes of vaccine tubes, I 
found at last, that with the smallest size I could produce a spray 
which, at about half an inch’s distance from any object, contained 
just as much ether as the given blast of air could evaporate. There 
was then of course no running of the ether to waste, while at the 
same time an intense cold was very rapidly produced. The method 
of adapting the spray points to one another is a modification of 
the ordinary one, and is adopted from a German model. It is as 
follows :—Two fine brass tubes are taken—one is brought to the 
requisitely fine point for the ether, and the other, being closed at the 
end, has the air-hole bored at the side a little below the closure. 
The point of the ether tube is then placed over the middle of the 
