16 DIFFERENT KINDS OF BARK. Chap. I. 



hexagonal cells filled with resinous matter and woody tissue. 

 In growing, the tree pushes out the bark, and, as the exterior 

 part ceases to grow, it separates into layers, and forms the 

 dead part or periderm ; which in chinchonas is partially 

 destroyed, and blended with the thallus of lichens. The bark 

 is thus formed of the dead part, or periderm, and the living 

 part, or derm. On young branches there is no dead part, the 

 exterior layers remaining entire, while the inner layers have 

 not had time to develop. In thick old branches, on the 

 contrary, the periderm or dead part is considerable, while the 

 fibrous layer of the derm is fully developed. In preparing 

 the bark the periderm is removed by striking the trunk with 

 a mallet, and the derm is then taken off by uniform incisions. 

 The thin pieces from small branches are simply exposed to 

 the sun's rays, and assume the form of hollow cylinders, or 

 quills, called by the natives canuto bark. The sohd trunk 

 bark is called tabla or plancJia, and is sewn up in coarse 

 canvas and an outer envelope of fresh hide, forming the 

 packages called serons. 



The character of the transverse fi-acture affords an im- 

 portant criterion of the quality of the bark. Cellular tissue 

 breaks with a short and smooth fracture, woody tissue with 

 a fibrous fracture, as is the case with the calisaya bark. 

 The best characteristics by which barks containing much 

 quinine may be distinguished are the shortness of the fibres 

 which cover the transverse fracture, and the facility with 

 which they may be detached, instead of being flexible and 

 adhering as m bad barks. Thus, when diy calisaya bark is 

 handled, a quantity of little prickles run into the skin, and 

 this forms one of its distinguisliing marks.'' 



Until the present century Peruvian bark was used in its 

 crude state, and numerous attempts were made at different 



7 Weddell. 



