620 JAMES W. BARRETT. 
cleared, and then in cacao butter melted at a temperature of 
35° C. for four to six or even twelve hours. At the end of this 
time it should be embedded in cacao butter in the usual 
manner. When the butter is quite hard, the sclerotic and part 
of the choroid should be detached with a sharp scalpel so that 
the retina and part of the choroid alone remain to be cut into 
sections, whilst the rod layer has never been tampered with. 
The retina should be fixed by pouring over it a little more 
melted butter which replaces the mass cut away. 
The sections may be cut either by hand, or with any ac- 
curately constructed “slide microtome,’ and with care may 
be made only one nucleus in thickness. Such sections are 
nearly invisible to the naked eye. If a microtome is used and 
such sections are prepared, they accumulate on the blade of the 
knife and look like a little mass of butter. This mass should 
be swept on to a slide, when the contained sections may be 
diffusely stained and mounted in the following manner : 
A few drops of an alcoholic solution of eosine are poured 
over the mass and at once soak into it; after a few minutes the 
mass is partially dried with blotting paper, and the slide is 
heated to a temperature of 35° C. The melted cacao butter 
is removed as far as possible with blotting paper, and a drop 
of oil of cloves is added to remove the remainder. When 
the sections are cleared a drop of balsam is added and the 
sections are mounted. 
It is very important to remove as much butter as possible 
before adding the oil, because the oil acts very violently and 
often destroys a section. In fact the great value of osmic and 
chromic acids as hardening agents depends largely on the 
great hardness they give to the retina, the sections of which are 
therefore not damaged by the oil of cloves. 
Conclusion.—I have been able to prepare the best sec- 
tions of retina by fixing and hardening in the watery solution 
of osmic and chromic acids in the manner described, staining 
in bulk with Kleinenberg’s logwood and infiltrating and em- 
bedding in cacao butter. 
Finally, I desire to acknowledge with sincere thanks the 
et sae 
