Cultivation and Ufe of the Syrian Silk-plant. T49 



trotluced into that aperture a delicate pair of fciffara, made 

 a fmal] hole in the iris, of the fize of a feed of forrel, indi- 

 cated in the engraving by the letter D. 



Through this hole, made in a non-tr&nfparent mem- 

 brane, the rays of light now enter, and form images on the 

 retina at the bottom of the eve. It is, therefore, an artificial 

 pupil which fupplies the place of that covered by the white 

 fpot of the cornea. But as behind this new pupil there is 

 no cryftalline humour to collect the rays with fuflicient 

 accuracy on the retina, C. Sauvages is obliged, in order to 

 'read, to make ufe of a very convex glafs, fuch as is ufed by 

 perfons who have undergone an operation for the cataract, 

 and who have loft the cryftalline humour, He does not 

 employ the glafs, however, except in cafes which require 

 more diftincl virion; and he (till poflbfles the invaluable ad- 

 vantage of feeing well enough to direct his way, and to 

 difcern perfectly every object around him. By means of 

 this ingenious operation, light in future may he reftored to 

 the greater part of thole who have loft that faculty by large 

 fpots or white fears, cafes hitherto confidcred as incurable; 

 provided that fome part of the cornea, opposite to the iris, haa 

 remained tranfparcnt. 



IX. On the Cultivation and XJfe of the Syrian Silk- Plant. 

 By J. A. Mull Kit, Director of the IVefphalian Patriotic 

 Society *, 



I. Defcription. -L HE filk-pTant, Afclepias Syriaca Lixx. 



known by the old botanifts and our gardeners under the 

 name of Apocynum Syriaatni, came originally from Syria 

 and Egypt. It is indigenous alio in Noith America, and 

 thrives fo well in Europe, that it would appear that it is 

 fuitcd for all countries and climates. The root is perennial, 

 and will laft from ten to twenty years. In the month of 

 April it throws out, like afparagus and hops, a great 

 number of (hoots, the principal Item of which rifes to the 

 height of feven or eight feet. This Hem, which is as thick 

 ■ From ilic TianfaRiom of t lye Academy aj the Ujejul Sennets ai 



aa 



