BELLADONNA RADIX 



379 



Powder. Microscopical elements of: See Part iv, Chap. I, B. 



CONSTITUENTS. The active principles are alkaloids, the chief of which are atro- 

 pine, hyoscyamine and hyoscine. Atropine is a compound of equal amounts 

 of the isomers, dextro- and levo-hyoscyamine into which it separates and is 

 readily changed to dextro-hyoscyamine. In the growing belladonna the 

 hyoscyamine is said to form in the young leaves, to be later changed to 

 atropine. 



According to the predominance of one or other of these alkaloids, and to 

 the amounts present, the drugs of this group fall into a regular pharmacologic 

 series, as follows: 



PIG. 217. Atropa belladonna Branch. 



1. Belladonna (root and leaves), the leaves containing 0.35 per cent., and 

 the root, 0.5 per cent., of alkaloid, which is nearly all atropine. It has, there- 

 fore, a typical atropine action. 



2. Scopola (root) contains 0.5 per cent, of alkaloid, about equally hyoscy- 

 amine and atropine. It acts like belladonna, but with somewhat less 

 strength. 



3. Stramonium (leaves) contains 0.35 per cent, of alkaloid, mostly hyoscy- 

 amine but with small amounts of atropine and hyoscyine. It is less stimu- 

 lating to the cerebrum and may be narcotic. 



