402 General Notes. [April 
their combinations, they become slightly granular, and remain 
so closely packed that it is difficult to distinguish the cell 
boundaries. Chromic acid, one- ee per cent. for three or four 
days, contracts the cells and es preparations in which the 
boundaries and general pa cit of the retinophore are 
easily studied. 
Sections of the Eye—In order to obtain the best sections 
of the adult eye with a% the parts in the most natural position, 
it is necessary to treat them first with one-tenth per cent. of 
chromic acid for half an hour, then in one-twentieth per cent. 
for twenty-four hours ; one-tenth per cent. for twenty-four hours, 
and finally one-fifth per cent. for forty-eight hours or more. 
Next to this method, it appears that solutions of sulphuric acid 
(twenty drops to fifty grammes of water) give the best prepara- 
tions (for acca Casa of everything except the rods. 
e double layer of the sclerotica and the fibres penetrating 
it can Tu seen in alete of eyes treated twenty-four hours in 
one-fifth per cent. chromic acid. 
Maceration and Dissection—The pigmented epithelial cells of 
Pectens’ eyes and the cells of the cornea are easily isolated by 
treatment with Miiller’s fluid or bichromate of potash one-half 
per cent. for two or three days. For the maceration of all other 
elements weak chromic or sulphuric acid is used, For the outer 
ganglionic cells, which are very difficult to isolate, maceration 
ne-fiftieth per cent. chromic acid gives excellent results, after 
previously fixing the tissue in one-fifth per cent. for a few minutes. 
For the vetinophore, one-twentieth per cent. for four or five 
days proves ve L 
Sulphuric acid, five drops to thirty grammes of sea-water, gives 
the best results for the nerve-endings in the retinophoræ (not in 
the rods).and for the nervous inner prolongation of the outer 
„ganglionic cells. 
In order to isolate pieces of the cornea with the subjacent 
seudo-cornea and the circular fibres, on the outer surface of the 
lens, it is better to macerate the eyes in sulphuric acid as given 
above. The same treatment retains to perfection the natural 
shape of the lens, which may then be isolated and its surface 
ye to advantage. 
for the study of the circular retinal membrane 
the septum, and the retina itself, to isolate the latter intact. 
aceration in chromic acid either makes the retina too brittle 
or too soft, while the axial nerve-fibres remain so firmly attached 
to the retina that it is difficult to isolate it without injury. But 
this may be easily and feninagpe d done by maceration for one 
or'two days in the sulphuric acid solution. By this peste 
ie setina, together bp the ee stom and circular retinal me 
brane, may be detached 
Surface vi of the retina show the peripheral outer gangli- 
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