934 Wisconsin Academy of Sciences, Arts, and Letters . 
sumably, the retort and condenser. Even with this modifica¬ 
tion, however, a large part of the solvent was still lost in the 
operation of straining. 
About this time (1820 to 1840), the extraction of drugs by 
the process of downward displacement was attracting consider¬ 
able attention, and, as the pharmacist saw in this procedure a 
means of eliminating the operation of straining, it is not at all 
surprising that it should have received early application in the 
preparation of the oleoresins. In explanation of the method of 
procedure as followed at the time, it should be stated that it was 
in reality a process of percolation under pressure, and, as such, 
required the use of a special form of apparatus. Two such 
forms were already available at the time when the oleoresins 
became a subject for investigation, namely: the Filtre-Presse of 
Real and the Luft-Presse of Romershausen. In fact, Geiger 
made use of the former in the preparation of the oleoresin of 
male fern as early as 1827. While these forms of pressure 
percolators eliminated the process of straining, their use, never¬ 
theless, appears to have been disadvantageous in certain other 
respects. For instance, the method of operation was rather 
cumbersome, and a considerable amount of solvent was absorbed 
by the cloth bag containing the powdered drug, thus rendering 
the apparatus of little value in working with small quantities 
of the latter. 
As a result of the early work with the pressure percolators, 
experimentation along this line was stimulated and it was soon 
shown that drugs could be completely extracted by simple per¬ 
colation under ordinary atmospheric pressures. The first evi¬ 
dence of the use of a simple percolator in the preparation of 
the oleoresins appears in Beral’s account of his preparation of 
the Piperoide du Gingembre in 1834. Fifteen years later 
(1849), Procter, in an article on the oleoresinous ethereal ex¬ 
tracts, mentioned two forms of simple percolators, a conical 
percolator made of tin, and Gilbertson’s displacement apparatus 
constructed of glass. Both of these were similar in essential 
detail to the percolators in general use at the present time. In 
fact, the United States Pharmacopoeia still directs that these pre¬ 
parations be made by simple percolation, a modified form of 
Gilbertson’s displacement apparatus being specified for use in 
this connection. This condition seems strange, indeed, in view 
of the fact that modern methods of operating with volatile 
