CRUDE DRUGS. 511 



thick, whitish, lemon-yellow or light brown, epidermis forming a 

 thin layer, mesophyll more or less shrunken, slightly crystalline 

 and with numerous circular projections of fibrovascular bundles ; 

 fracture brittle when dry, tough when damp; odor slight; taste 

 bitter and acrid. 



Constituents. — Squill contains a number of active principles, 

 of which the most important are the amorphous glucoside scilli- 

 toxin, which resembles digitoxin physiologically, and scillipicrin, 

 an amorphous, bitter principle, which is employed as a diuretic. It 

 also contains a yellow crystalline glucoside scillin ; an amorphous 

 bitter glucoside, scillain ; a little volatile oil ; sugar, about 22 per 

 cent.; considerable calcium oxalate in the form of raphides (Fig. 

 281, B), which is associated in the parenchyma cells with a 

 peculiar mucilage sinistrin, which yields levulose on hydrolysis. 



Allied Plants. — The bulbs of several species of Crinuin 

 (Fam. Amaryllidaceae) found growing in Brazil, China, Southern 

 Asia and the East Indies are used as substitutes for squill. 



III. PARTS OF ROOTS AND STEMS. 

 PITH, WOOD .\ND BARK. 



The active principles are not uniformly distributed throughout 

 all parts of the plant, but occur in greater amount in the bark 

 than in the wood, as in Ipecac ; in larger proportion in the root 

 bark than in the stem bark, as in Granatum ; and in larger amount 

 in the inner bark and cortex than in the periderm layers, as in 

 Quercus alba. This is in general true of herbaceous plants, as 

 well as of trees and shrubs, but in most of the medicinal roots and 

 rhizomes it has not been found economical to separate the bark 

 from the wood, which usually contains some of the active prin- 

 ciples. A large number of the barks alone of shrubs and trees are 

 used medicinally. By the term bark is usually meant all that 

 portion of the root or stem which is developed outside of the cam- 

 bium, and this is commonly differentiated into two distinct parts — 

 one next to the cambium, in which the life-processes take place, 

 contains the greatest amount of active principles, and is known 

 as the INNER BARK (Figs. 227, 231, 234) ; another, external to 



