PREPARATION OF BYE FOR HISTOLOGIOAL EXAMINATION. 619 
with a nuclear stain should be stained (best on the slide) with 
either fuchsin or an alcoholic solution of eosin, preferably the 
latter. The exact method of staining will be described. 
Mode of Preparing and Mounting Sections.—Sec- 
tions may be obtained by : 
1. Infiltrating and embedding in celloidin and freezing. 
2. Infiltrating and embedding in celloidin and cutting under 
spirit. 
3. Infiltrating and embedding in paraffin. 
4, Infiltrating and embedding in cacao butter. 
1 and 2. It is difficult to obtain thin sections by the second 
method, but very fair ones may be obtained by—(1) the whole 
sclerotic, choroid and retina should be embedded together, and 
when the celloidin is firm the retina and part of the choroid 
should be separated with a sharp scalpel; attempts to separate 
the retina earlier generally end in damage to the rod layer. 
After the sections have been cut by the method previously 
described they may be diffusely stained and mounted. The 
staining may be effected in two ways: (a) to the water in which 
the sections have been placed on removal from the microtome 
a little eosin is added; in a few minutes they will be suffi- 
ciently stained; or (4), they may be at once placed on the 
slide with a section lifter and the staining may be effected 
there. In either case after staining they should be gently 
washed and nearly dried with blotting paper, then covered with 
a few drops of alcohol. On removing this reagent with blotting 
paper they should be cleared either in oil of cloves or oil of 
bergamot and may be mounted in balsam. 
3. By the paraffin method already described aerial sections 
may be prepared, but I have never yet obtained by this 
method any sections of very great histological value; they have 
been at best passable. 
4. Infiltrating and embedding in cacao butter. By this 
method I have been able to prepare the thinnest and best 
sections of retina with a minimum amount of trouble. A 
piece of the eye stained with a nuclear stain should be placed 
first in alcohol until dehydrated, then in oil of cloves till 
