( *440 
I. Microfcopical Obferyatiom on the Cortex Peru- 
vianus : By Mr. Anthony Van Leeuwenhoek, 
F. % S. 
I Have been many Years acquainted with the Heer An- 
gel* s Van Wikhnyfen, a Do&or of Phyfickat Midd'e- 
burgh in Zealand, and I have a much greater efteem for 
him, becaufe he has owned to me feveral times, (and fo 
indeed have divers other Learned Gentlemen,} that he 
knew very little of the Art of Healing, and that moft of 
his Operations were performed by fimple Medicines. 
When this Gentleman came to vifit me laft, our Dit 
courfe fell again upon the Skin or Bark of that Tree, 
which is called China China, and which is made ufe of 
with fuccefs in the moft Obftinate Fevers. 
Our Difcourfe amongft other things rolled upon this 
Topick, That between one Bark and another there is a 
great deal of difference ; for in all Woods that are known 
tome, the Bark proceeds out of the Wood, and every 
Year there is produced a new Bark between the Wood 
and the old one of the former Year, by which means the 
Barks of Trees grow every Year thicker and thicker; fo 
that at length the extreameft Bark that lies fartheft from 
the Tree does not only receive no nourifhment, butal- 
fo dies,fo that that which before had a tafte in it, becomes 
altogether taftlefs, as I have {hewn : pon other Occafions ; 
and consequently thofe Barks, which we call china china , 
are beft when feparated from the youngeft Trees. 
Hereupon the Do&or frankly Communicated to me, 
how he made ufe of the China China , adding, that he 
thereby 
