PREPARATION OF EYE FOR HISTOLOGICAL EXAMINATION. 617 
dark. At the end of twenty-four hours the reduction was 
complete. This process is a modification of that which Mr. 
Underwood employs with great success in the preparation of 
sections of teeth. 
d. The fresh freely-opened eye was placed in a solution of 
osmic and chromic acids (afterwards described) for two to five 
days and was then treated as inc. By noneof these methods 
have I been able to procure one satisfactory section. 
10. Osmic Acid.—By means of this very reliable reagent 
I have obtained my best results. 
a. The fresh and opened eye was placed for twenty-four to 
forty-eight hours (not longer) in a watery solution of osmic 
and chromic acids; + per cent. chromic acid, ;4, per cent. 
osmic acid. It was then placed in the mixture of alcohol and 
carbolic acids for fourteen days or more. By this process the 
retina was rendered exceedingly hard but not brittle. The 
sections showed the structure of all parts of the retina, the 
rods being sharply defined and remaining in siti. (One of 
these sections was exhibited at the December meeting of the 
Physiological Society, 1885.)! If the retina was allowed to 
remain in the solution for more than forty-eight hours brittle- 
ness was usually produced. 
6. The fresh and opened eye was placed in a ‘75 to 1 p. c. 
solution of osmic acid for from thirty minutes to twelve hours, 
and was subsequently treated with (a) alcohol, glycerine and 
water, or (0) alcohol, or (c) alcohol and carbolic acid. The 
hardening was not usually good and the results were often 
only passable. 
c. In order to obtain very rapid penetration of the retina by 
the fixing agent, solutions of osmic and chromic acid in 
alcohol were employed. 
They were: 
1. Osmicacid . + per cent. 
Chromic acid . re 
Commercial alcohol } 
> § Equal parts. 
Water, Cigars 
B|- 
1 * Proceedings Physiological Society,’ December, 1885. 
