SECTION VI 

 WOODS 



Under this heading are grouped together a number of drugs con- 

 sisting of the wood of the trunk, branch, or root of trees. Medicinal 

 woods are derived from dicotyledonous plants, and the following 

 structural details which may be of assistance in identifying woods 

 apply to those of dicotjdedonous origin. 



1. Medullary Eays. These are best examined on a smooth trans- 

 verse and tangential section. On a transverse section they appear 

 as fine, continuous lines radiating from the centre to the periphery. 

 They vary in width in different woods and also frequently in the 

 same wood ; the wide ones are usually visible to the naked eye, but 

 they are best examined under the lens. The distance between the 

 rays also varies with the different woods, a variation which may 

 be indicated by stating the number of rays that occur in 5 mm. of 

 the wood. 



2. Vessel^. The size and distribution of the vessels also afford 

 valuable information. The vessels in the spring wood are usually 

 larger and more numerous than those in the autumn wood, and hence 

 more or less well-defined concentric lines are produced ; in some 

 woods, however, the distribution is irregularly radial. They are 

 often large enough to be visible to the naked eye (over 0-1 mm.), 

 frequently, however, scarcely perceptible even under the lens (under 

 0-02 mm.) ; they may occur singly or be arranged in radial or tangential 

 groups of two or more. 



3. Parenchyma. The parenchymatous tissue of the wood may 

 also exhibit a characteristic distribution usually assuming the form 

 of mor3 or less distinct concentric circles (false annual rings). 



The woods dealt with in the succeeding section are easily dis- 

 tinguished from one another by their colour, odour, or taste, but 

 the student should examine them carefully with the lens, as above 

 described, in order to distinguish them from other similar woods that 

 might be substituted for them. 



