46 VEGETABLE DRUGS WITHOUT ORGANIC STRUCTURE. 



chloral hydrate, 60 per cent, solution. Some, particularly 

 the fossil resins, simply swell up. Chloral hydrate, 60 

 per cent, solution, is one of the few solvents that puts 

 both gum and resin in the gum resins into solution. 



As to the formation of the resins in plant tissues it is 

 enough to know that they exist either in special secretory 

 channels, usually in the woody portions of the plant, 

 or they flow into the tissues and make artificial passages 

 for themselves. As to the origin of the resins, they may 

 be considered in part as retrogressive metamorphic 

 products, largely from tannins, cellulose and from starch, 

 but there are many exceptions. 



Chemically it has been pointed out already that the 

 resins are extremely complex, as would be supposed 

 when one considers the different sources from which 

 they may come. The whole subject is a fascinating 

 one, yet very complicated. It may be considered, how- 

 ever, that many of the resins start as oxidized products 

 of some of the terpenes. In fact, most of the resins 

 show series of compounds, as esters, alcohols, etc., that 

 shows either their origin from volatile oils, or a like 

 origin for each class of compound by metamorphosis of 

 the cellulose and starch constituents in the cell wall or 

 in the cell body. Polymerized terpenes seem abundant 

 in the resins (C5H3, C^^H,^, Ci^H^^, C^.K^^). Sesqui- 

 terpene (C15H24) is present in a number of resins — Cade, 

 Galbanum, Olibanum, Asafetida, Copaiba. 



Thus it becomes evident that in this class of bodies 

 one finds a closely allied series of compounds of like 

 though varying composition, and it would be natural 

 to suppose that pharmacologically and therapeutically 

 they form allied groups. This is the fact, and if the 

 knowledge of the elementary composition of a drug 

 teaches that one has to deal with certain volatile oils 

 or resins or balsams, then one knows at once what may 

 be expected pharmacologically and therapeutically. 



