614 JAMES W. BARRETT. 
The sections were prepared in the first set of experiments 
by infiltrating and embedding in celloidin in the manner already 
described. 
The following fixing and hardening solutions were 
employed : 
1. Miller’s Fluid.—The fresh eye, opened in the way 
already described, was placed in Miiller’s fluid for two or three 
weeks, during which time the fluid was changed as often as its 
altered appearance afforded an indication of the necessity. It 
was then transferred, after being washed, to strong commercial 
alcohol, and was completely hardened in about two weeks. 
Sections of retinas so prepared were serviceable in showing 
the structure of the inner layers of the retina and the course 
taken by the blood-vessels (in retinas which contain them), but 
the rod-and-cone layer and the outer nuclear layer were more 
or less completely destroyed. 
2. Bichloride of Mercury.—A saturated watery solution 
was employed; the freshly opened eye was placed in this solution 
for three to six days, and was then hardened in alcohol as 
before. Some eyes I placed in alcohol containing 2 per cent. 
of carbolic acid instead of simple alcohol. 
The salt “ fixed” in a manner much superior to Miiller’s 
fluid, but usually permitted or caused shrinkage in the rod 
layer. 
The sections of retinas prepared with the alcoholic solution 
of carbolic acid were superior histologically to those prepared 
in alcohol alone, and this I found to hold good for all the 
fixing agents employed. 
It occured to me at this stage of my work that possibly the 
fixing solution did not gain access to the retina with sufficient 
rapidity, the opening in the eye not being large enough; yet a 
very large opening allows the retina to become detached. 
I therefore procured two cannule, and pushed them through 
the coats of the eye into the vitreous at points a little distant 
from one another; then I endeavoured to fill the vitreous with 
the fixing agent by injecting it through one of these cannule 
whilst the intraocular tension remained unaltered. 
