PRUNUS VIRGINIANA 



215 



periderm, but bark collected from the older parts usually has the 

 corky layer removed, leaving a rough, rust-brown surface, inner 

 surface lighter colored, finely stria te; fracture granular. Almost 

 inodorous, but emits the characteristic odor of bitter almonds when 

 moistened; taste astringent, aromatic, and bitter, at the last bitter 

 almond-like. 



STRUCTURE. Beneath the corky layer are found numerous clusters of 

 stone cells, forming an interrupted zone. Just beneath this layer the 

 medullary rays, which in the whole bark are wavy, terminate very 

 obliquely. Between the medul- 

 lary rays are found masses of 

 stone cells and more elongated 

 bast fibers. 



The bark of the root is thought 

 to be the most active, but that 

 of the whole tree is collected in- 

 discriminately. 



RELATIVE VALUE OF THE OLD AND 

 NEW BARK. Experiments by 

 Dohme and by Stevens have 

 been made to decide whether 

 the green bark is richer in hydro- 

 cyanic acid than the older, thick, 

 brown bark. The results of the 

 experiments of these gentlemen 

 are somewhat contradictory. 

 Dohme obtains 0.216 and 0.183 

 per cent, of HCN respectively, 

 while the older bark assays 0.167 

 and 0.159 P er cent. Stevens 

 found in the older bark 0.335 

 per cent., while the younger 

 assayed only 0.25 per cent. It 



is probably safe to say that the older thick bark is not so unworthy 

 of recognition as some believe. 



Powder. Characteristic elements: See Part iv, Chap. I, B. 



CONSTITUENTS. Tannin, a bitter glucoside, resin, starch, etc. The vola- 

 tile oil and hydrocyanic acid, to which the sedative action is due, do 

 not preexist in the bark, but, as in the bitter almond, are formed by 

 the action on amygdalin, in the presence of water, of a ferment an- 

 alogous to, if not identical with, emulsin; the action of this ferment is 

 destroyed at a boiling temperature, and therefore heat should never 

 be used in making preparations of this bark. 



FIG. in. Cross-section of bark of stem of 

 Prunus Virginiana (P. serotina). A. Cork. 

 B. Middle or green layer of bark. C. 

 Clusters of stone cells. D. Compressed 

 sieve tissue. E. Medullary ray. F. Fis- 

 sure between medullary ray and bast. 

 G. Bast tissue. H. Cambium zone. /. 

 Ducts in mature wood. 



