20 
ON THE ASCLEPIAS CURASSAVICA. 
bearing the most distant resemblance to it, producing white 
blossoms, since I quitted Hayti. The Haytian plant ap- 
pears in the form of its leaves to correspond with Plumier's 
Jlpocynum Smericanum Jimygdalifoliis longioribus,sp. 
2, I.e. 30. I met it in blossom in the months of June, July, 
and August ; but while the Asclepias nivea is so abundant 
near the Cape, I experienced the greatest difficulty in ob- 
taining a specimen of the Asclepias curassavica, which is so 
very common at Nevis and St. Kitts. Of the properties of 
the Asclepias with white blossoms, I can find no memoran- 
dum among my papers, but believe they" were not re- 
garded as different from those of the Redhead. 
The root of this last contains an emetic principle, varying 
so much in the degree ofits activity, as to render its opera- 
tion dangerous and uncertain; and has hence occasioned its 
dismissal from regular practice. Among the poorer whites 
and blacks, however, it is occasionally employed as a cheap 
substitute for Ipecacuanha, the powdered root being ad- 
ministered, after having been previously infused in warm 
water and then dried, in doses of from one to two scruples. 
The same emetic property resides in the expressed juice, 
which is exhibited internally to the extent of an ounce or 
more. 
The uncertainty which attends the emetic operation of 
this plant arises most probably from inattention to the proper 
season of gathering it; a similar uncertainty attending all the 
more active articles comprising our Materia Medica, which 
are derived from the vegetable kingdom ; of which the Pis- 
cidia erythrina in the West Indies, and the Digitalis purpu- 
rea, and Colchicum autumnale in Europe, furnish familiar 
examples. The age of the moon also is another circum- 
stance which demands consideration in connection with the 
season of the year ; since whatever sceptics, whose range of 
observation has been confined within the limits of the tem- 
perate zones, may think, all who have a practical acquaint- 
ance with the perennial vegetation of the topics, are fully 
