166 A TEXT-BOOK OF BOTANY. 



sels in 1902 a protocol was prepared designating the strength of 

 the various galenicals. Unfortunately, a standard for the alka- 

 loidal content of drugs was not also established, and consequently 

 in the several pharmacopoeias there is still some variation in drug 

 standards. For percentage of alkaloids in different drugs and their 

 variation, consult Volume II, treating of Pharmacognosy. 



CHEMICAL CLASSIFICATION OF ALKALOIDS. The chemical 

 study of the alkaloids shows that each plant contains not one but 

 a number of alkaloids, cinchona bark and the opium poppy yield- 

 ing not less than twenty different alkaloids. As their chemical 

 constitution is not well known, it is customary even for the chemist 

 to group them into certain natural classes, as the alkaloids of 

 conium, tobacco alkaloids, the cinchona alkaloids, opium alka- 

 loids, etc. They may also be grouped into certain fundamental 

 groups, according to their nuclear structure derived from their 

 probable constitution. While the natural classification may be 

 more convenient, it will be replaced by a classification based on 

 chemical constitution when our knowledge of this class of sub- 

 stances is extended. From studies thus far made the following 

 groups of alkaloids may be recognized : 



PYRIDINE GROUP. Alkaloids derived from pyridine (C 5 H 5 N) 

 are found in Conium maculatum, Piper nigrum, and other species 

 of Piper, Trigonella Fccnum grcccum, Areca Catechu, Beta vul- 

 garis, Nicotiana Tabacum, Pilocarpus Jaborandi and other species 

 of Pilocarpus, Lupinus, Laburnum, and other genera of the 

 Leguminoscc. This group includes the liquid or volatile alkaloids. 



PYRROLIDINE GROUP. Derivatives of Pyrrolidine (C 4 H 8 NH) 

 occur in Atropa, Hyoscyamus, Datura, Scopolia and other genera 

 of the Solanacece, Erythroxylon Coca, and Punica Granatum. 



QUINOLINE GROUP. Alkaloids with a Quinoline nucleus 

 (C 9 H 7 N) are obtained from cinchona bark and nux vomica. 



ISOQUINOLINE GROUP. Isoquinoline is isomeric with quino- 

 line ; alkaloids with this nucleus are found in the opium poppy, 

 Hydrastis canadensis, Berberis vulgaris, Menispermum canadense 

 and quite a number of genera in the closely related families of 

 Ranunculacecc, as well as in some other plants. 



PHENANTHRENE GROUP. Morphine and codeine, closely re- 



