142 PHILOSOPHICAL TRANSACTIONS. [aNNO 1737. 



An Account of the Peruvian or Jesuit's Bark.* By Mr. John Gray, F. R. S. at 

 Carihagena, from some Papers given him by Mr. William Arret, a Scotch 

 Surgeon, who had gathered it at the Place where it grows in Peru. 

 N°446, p. 81. 



The tree from which the Jesuit's bark is cut, grows in the kingdom of Peru, 

 in the Spanish West Indies, and is found most commonly in the provinces of 

 Loxa, Ayavaca, and Quenca, situated between 2 and 5 degrees of south lati- 

 tude. This tree is tall, and has a trunk rather thicker than a man's thigh, taper- 

 ing from the root upwards; it has no boughs or branches, till near its top; 

 where they grow as regular as if lopped artificially, and with the leaves form 

 exactly the figure of a hemisphere : its bark is of a blackish colour on the out- 

 side, and sometimes mixed with white spots; whence commonly grows a kind 

 of moss, called by the Spaniards, barbas; its leaves resemble much the leaves 

 of our plum-tree, are of a darkish green colour on their upper or concave side, 

 and on their lower or convex side, reddish ; its wood is as hard as common 

 English ash, and rather tough than brittle. 



There are 4 sorts of the bark of this tree, to which the Spaniards give the 

 following names, viz. cascarilla colorada, or reddish bark ; amarylla, yellowish ; 

 crespilla, curling; and blanca, whitish; but Mr. Arrot could only find 2 dif- 

 ferent sorts of the tree, and he believes that the other 2 sorts of the bark are 

 owing to the different climates where it grows, and not to a different species 

 of the tree. The bark called colorada and amarylla, is the best, and it differs 

 from the blanca in this, that the trunk of the former is not near so thick as that 

 of the latter; the leaves as described above; whereas those of the blanca are 

 larger, and of a lighter green colour, and its bark has a very thick spongy sub- 

 stance, whitish on the outside, and is so tough, that it requires the force of an 

 axe to slice it from the tree. It is as bitter when cut down as the best sort, 

 and has then the same effect in intermitting fevers; but when dry and long kept 

 it turns quite insipid, and is good for nothing. Both sorts have a much surer 

 and quicker effect in cures when green than when dry. As the bad sort is in 

 great plenty, and the best very scarce, and hard to be come at, large quantities 

 of it are cut yearly, and sent with a little of the fine bark to Panama for 

 Europe. 



The tree of the crespilla is the same with that of the amarylla and colorada, 

 but it grows in a cold frosty climate { by which means the bark is not only altered 

 in its quality, but is also whitish on the outside, though cinnamon-coloured 



* Cinchona otHcinalis. Linn. 



