ON THE PREPARATIONS OF SENEKA. 249 
subaeetate of lead, washing the precipitate with water, 
suspending it in that fluid, and the lead precipitating by a current 
of sulphuretted hydrogen. The filtered liquid is then evaporat- 
ed 8 to an extract, this exhausted by boiling alcohol 40° Baume, 
and the extract resulting from the evaporation of this alcoholic 
fluid treated with water, which takes up the polygalic acid and 
leaves a yellow matter. The solution containing the polyga- 
lic acid is again treated with subaeetate of lead, sulphuretted 
hydrogen and evaporation, and the extract obtained is dissol- 
ved in boiling strong alcohol which deposites the polygalic 
acid in a pure state by cooling. 
Polygalic acid may be obtained pure enough for medical 
use, by treating the powdered seneka with boiling alcohol of 
35° Baume until exhausted, removing the alcohol by distilla- 
tion until the fluid is reduced to a syrupy consistance, then 
treating it with ether to remove fatty and resinous matter, and 
mixing with a quantity of cold strong alcohol — which, by stand- 
ing several days, precipitates the acid of a light brownish colour. 
In this state it is impure, and requires to be redissolved in hot 
alcohol boiled with animal charcoal and filtered while hot. 
When it separates in a pulverulent form, M, Quevenne has 
proposed the employment of polygalic acid as a therepeutic 
agent and from its easy preparation and great activity, there 
appears no good reason why it should not be added to the list 
of medicinal proximate principles. The physician would be 
enabled to control the action of the remedy more completely, 
and by combining it with other substances, to modify its in- 
fluence. The patient would be less inconvenienced by its ad- 
ministration, as its concentrated form admits of its being more 
easily disguised in mucilage in syrup or in pill. 
From an approximative estimate, M. Quevenne infers that 
one grain of polygalic acid represents the activity of a dram 
of seneka. 
The following formula would represent an ounce of the 
root and a pint of decoction, or four fluid ounces of the syrup : 
