H. Goadby on making wet Preparations of Animal Substances. 15 
Art. IIl.—Instructions for making wet Preparations of Animal 
Substances ; by Henry Goapsy, M.D., F.L.S., formerly Dis- 
sector of Minute Anatomy to the Royal College of Surgeons 
of England. 
If the object be merely a filmy tissue, take a piece of glass of 
good quality, good surface, and flat ; the substance is not mate- 
rial.* Clean it with liqnor potasse or dilute sulphuric acid, or 
use both these fluids, mixing them on the glass; they eflervesce, 
ecompose each other, and at that moment, clean the glass; rinse 
it in clean soft water and dry it with either a clean muslin hand- 
kerchief, or a piece of chamois leather ; now test it witha drop of 
water placed on the center of one side of the glass, and if the 
water can diffuse itself evenly over the whole surface, the glass is 
clean ; if not, it must be made so. 
This, which is frequently the most difficult part of the whole 
process, being accomplished, place the glass in the vessel in 
which the tissue to be mounted lies in preserving fluid, and float 
it on to the glass; withdraw the latter carefully from the vessel, 
With a fine (needle) point adjust the tissue to the center of the 
glass, and soak up the excess of fluid with a camel’s hair pencil, 
leaving enough to cover the preparation. Now take a piece of 
thin glass, snch as is used by microscopists, previously cut of 
less width than the slide or glass on which the tissue lies, and 
having cleaned it by the mode described, hold it at one end bya 
pair of finely pointed forceps, and apply the other extremity, hold- 
ing it almost vertically, to such portion of the other glass as to 
leave the preparation in the center of both. 
_ Gradually lower the top glass, and the fluid will run before it 
until the preparation be covered, and the top glass finally rest 
upon the lower one. 
A quantity of fluid will yet remain outside the top glass which 
must be carefully taken up with the camel’s hair pencil until the 
am, ried 
that neither acid, nor potash can clean a piece of glass 
e it to endure the test Lads erate in such case a watery so- 
arabic may be'used, or, what is still, better—the human saliva will 
