VEGETABLE POWDERS. 



depends, in great measure, upon the variations in the form and 

 size of the starch grains they contain, but the tissues of the 

 seed-coats and pericarps also exhibit notable features. 



The officinal powders are much more numerous and more 

 varied, as well as more complex in their composition. Their identi- 

 fication is attended with considerable difficulty, the more so as 

 it requires a more or less complete knowledge of the structure 

 of the drug that has been powdered. They may be divided into 

 the following classes, according to the nature of the organ from 

 which they have been prepared viz., leaves, flowering tops, 

 flowers, seeds, fruits, barks, rhizomes, roots and woods. Each of 

 these classes possesses fairly well-marked distinctive characters. 



The question may well be asked whether the vigorous grind. ng 

 to which the drugs are subjected during the process of pulverisa- 

 tion does not crush and completely destroy the elements of which 

 they consist, and thus render any morphological or anatomical 

 study of them futile. It cannot be denied that the so-called 

 impalpable powders are more difficult to identify than those pre- 

 pared by the pharmacist in his own laboratory, but nevertheless 

 each one of them contains certain elements that even the most 

 prolonged trituration will fail to destroy and that serve to 

 identify the powder. 



During the pulverisation of a drug, the different layers of which 

 it consists are usually separated as such from one another ; thus 

 parenchymatous, sclerenohymatous, and fibrous elements are 

 separated from one another, but each of them retains its form and 

 characteristics. But it often happens that even long-continued 

 grinding fails to separate layers that abut upon one another. This 

 may be frequently observed in the powders of fruits and seeds* 

 in which two, three, or even four layers may be found adhering 

 together in the same relative position that they occupied in the 

 original drug (linseed, pepper, wheat). 



Thin-walled parenchymatous cells are frequently broken open 

 by the trituration, and their contents are thus allowed to escape : 

 this accounts for the presence in vegetable powders of isolated 

 starch grains and calcium oxalate crystals, the various shapes of 

 which often aid one ir the identification of the powder. Elements 

 of greater solidity, such as vessels, tracheids, and fibres are often 

 not only separated from other elements, but broken into frag- 

 ments ; as, however, these elements are generally elongated and 

 exhibit the same characters throughout the whole of their length, 

 each fragment will usually preserve the distinctive features of the 

 element of which it is a part. 



Sifting does not appreciably complicate the identification oi 

 vegetable powders, as its action is usually confined to the separa 

 tion of the larger particles of tissue from the smaller, and seldom 

 results in the removal of isolated elements. 



