4 
PREFACE. 
this volume something more than a mere compilation 
of others’ work, therefore some of his own experience 
has been incorporated which is here published for the 
first time, and this will be kept constantly in mind 
during the further contributions on the subject. 
The tannins occupy a part of the border-land in sci¬ 
ence between botany and chemistry, which fact has 
added to the bulk of the literary index as well as to 
the difficulties of collecting it. 
However, by the aid of the many complete sets of 
valuable foreign chemical periodicals recently acquired 
by the library of the Franklin Institute, and also 
through constant access to the library of the Phila¬ 
delphia College of Pharmacy, it has been possible to 
take from the original sources all but about five per 
cent, of the titles given. Such references as could not 
be so consulted were taken from the most available 
source, and, if possible, in the same language as the 
original. 
It is with the hope that information will be received 
from others interested in the subject, which will assist 
in making the index more complete, that it is issued at 
the present time. 
Much valuable assistance has already been received 
by the author, especially from those having desirable 
private libraries, for which he hereby tenders his sincere 
thanks. 
Philadelphia, November 13, 1891. 
