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L. RANVIER. 
On the Terminations of Nerves in the Epidermis. By 
L. Ranvier, Professor at the College de France. With 
Plate XXXVI. 
It is well known that by the employment of chloride of 
gold it is possible to show the ultimate nerve-endings in 
tissues. But this reaction is not always followed with suc- 
cess if the original process of Cohnheim is pursued ; and in 
attempting, during the last few years, to render it more 
regular by combining the action of the gold with formic acid, 
Pritchard and Loewit have effected a very notable progress. 
At the same time the process of Loewit, although it gives far 
more constant results than any previous process, is not 
without its disadvantages. The solution of a third part of 
formic acid, in which the tissue is placed before being sub- 
mitted to the action of the gold, alters the ultimate ramifica- 
tions of the nerves, so that, on being fixed by the action of 
the gold, they are more or less altered. 
It occurred to me that, in the simultaneous action of 
formic acid and chloride of gold, the latter reagent would 
retain its selective power, and by the rapidity of its action 
would prevent the nervous terminations from being seriously 
injured by the acid. It appeared to me also important that 
the reduction of the gold should be as rapid as possible. 
These considerations led me to the following process. 
The tissues, with the nerve terminations, are placed in a 
mixture of chloride of gold and formic acid, which has been 
boiled and then cooled. After remaining in this mixture 
between two and four hours they are removed and washed, 
and the reduction of the gold is effected either by the action 
of daylight in slightly acidified water, or in the dark in a 
solution of formic acid. 
By this method of treatment the terminations of the 
nerves in muscles appear continuously arborescent, instead of 
being frequently interrupted, as they are when the process 
of Loewit is employed. At the same time they contain some 
irregularities which prove that the process is still insufficient. 
For this reason it became necessary to invent a fresh process. 
I attempted to replace formic acid by an acid which would 
not have an equally deleterious effect on delicate elements, 
and believe that I have found it in the juice of the lemon. 
Lemon juice, though its protracted action alters nervous 
tissues, yet preserves their form sufficiently long for it not 
to be altered in the time requisite to procure the whole effect 
