BY J. M. PETRIE. 131 



How are these variations to be explained? Ladenburg has 

 stated that they were due to different methods of manufacture, 

 but he believed that his hyoscine was a true isomer of hyoscya- 

 mine, and therefore his opinion was legitimate. We are now 

 certain that these two bases possess a different chemical com- 

 position, and therefore cannot be transformed in this way, so 

 that Schmidt's view was nearer the truth— that the leaves some- 

 times contained hyoscyamine, and at other times scopolamine. 

 Our present biochemical knowledge, however, will scarcely 

 admit of this view, that a plant under variable conditions may 

 alter its fundamental chemical products. But it is quite pos- 

 sible that variations in the conditions of growth influence the 

 relative amount of each of these bases, by stimulating and 

 causing a predominance of one, or by reducing the production 

 of another to a minimum amount. 'J he plants probably contain 

 all the alkaloids in question, and none is entirely absent at any 

 time. The detection of the small amounts of one of these 

 alkaloids in the mixture requires the greatest skill and patience, 

 and in most of the papers cited the authors omit the details of 

 manipulation by which alone the value of their results can be 

 estimated. 



This example of the variation of the tropeines in the Duboisia 

 is analogous to that of the cocaines in Erythroxylon, and to the 

 strychnine and brucine in the Strychnos plants. 



Chemical composition compared. 



xix. The two Duboisias, whose history we have been tracing, 

 are thus shown to contain the widely different active principles, 

 nicotine and hyoscyamine, while the original botanical descrip- 

 tions of the two plants have much in common. 



Tn order to bring ont any further points of interest in the 

 comparison of these two plants, a complete chemical analysis of 

 the proximate constituents was made. 



In each case, the air-dried leaves were submitted to successive 

 extractions with organic solvents, and the extracts further 

 analysed. The results of these analyses are given in the accom- 

 panying table. 



