304 THE MIcRoscoPr. 
cat appears to be surprised at the peculiar smell of the chloro- 
form, much the same as is a human being who is compelled to 
inhale it for the first time. The animal makes attempts to es- 
cape, but her efforts are rendered futile by the smoothness of the 
glass. Soon she will become unconscious, will tumble to the 
floor and die in a few minutes without a struggle, if a sufficient 
quantity of choloform be used. 
With a pair of scissors the cornea is rapidly cut out, not too 
near the body of the sclerotic, placed in a dilute solution of lactic 
acid of about ten per cent, strength and left in this solution for 
about twelve hours. After the lapse of this time the cornea is 
transferred into a saucer filled with a solution of chloride of gold, 
not stronger than half of one per cent. and slightly acidulated 
by the addition of a few drops of lactic acid. While the speci- 
men is exposed to the chloride of gold, the light should be shut 
off from it by a towel spread over the cover of the saucer. After 
two hours’ exposure to the reagent, the cornea is transferred into 
a flat plate filled with distilled water, and by means of two deli- 
cate forceps is split up into the thinnest possible lamelle, about 
forty of which will be furnished by each cornea. The lamelle 
thus obtained are mounted in chemically pure glycerine, pre- 
ferably that of Merck which, though costly, serves our purposes 
best. The thinnest cover glass should be used. In a day or 
two, after which time the specimen remains exposed to broad 
daylight on a sheet of white paper, and after thorough cleansing 
around the borders of the cover glass with folded up Swedish 
paper, the sealing may be accomplished by means of asphalt or 
any other varnish. The specimen, in the meantime, will have 
assumed a pale violet tint along the border that has been directly 
under the influence of the lactic acid. This border is unfit for 
research, since its features are destroyed by the acid. The cen- 
tral portions will show a dark violet hue, if the hght passes 
through it, and a golden film by reflected light. 
I must justify every step I have advised. I have given pre- 
ference to the cat’s cornea, because we know that this is one of 
the best subjects for our purpose, although the cornea of a rab- 
bit, a rat, or a frog is equally good and equally cheap. The 
study of all these animals’ corneze, including that of man, shows 
identity in all minute features. Even the cornea of a fish will 
furnish, in its central portions, identical results. 
