284 PROFESSOR C. R. MARSHALL ON 



light is the part which the constituent groupings play in the pharmacological action of 

 tropeines. Buchheim,* LADENBURG,t and others have found that various aromatic 

 acidic groups could be attached to the base tropine, and an atropine-like action 

 be obtained ; whereas Crum Brown and Fraser,| and more recent observers, have 

 shown that alterations in the tropyl radical generally produce profound changes in the 

 pharmacological action of a tropeine. This suggests that the fundamental action of 

 these tropeines depends on the tropyl radical, and that the interaction with the so- 

 called nerve endings occurs through the mediation of the acidic grouping. Whether the 

 acidic group has any other action than a connecting or haptophoric one with the tissues 

 is difficult to decide. Many of the tropeines, in so far as they have been investigated, 

 differ little except quantitatively in pharmacological action from atropine, and it is open 

 to assume that in these compounds the acidic groupings are purely haptophoric in 

 character, since their different quantitative effects might be explained by differences in 

 the power with which the acid group is able to attach the tropyl group to the nerve 

 endings. Gottlieb, § however, showed that certain tropeines act very differently from 

 atropine — acetyl-tropeine causes convulsions and succinyl-tropeine paralysis, and neither 

 affects the vagus endings or the pupil ; and in view of the comparatively simple nature 

 of the acid groups of these compounds, it seems questionable whether any distinctive 

 action can be attributed to the constituent groupings of tropeines. In the case of 

 protocatechyl-tropeine we have a compound which differs materially in action from 

 other tropeines, yet most of its actions can be demonstrated with atropine. But while 

 it acts much less powerfully than atropine upon the vagal endings in the heart, it acts 

 more powerfully on voluntary muscle, and has an action on the respiratory centre which 

 atropine shares to a relatively slight degree. It may be that these differences might be 

 explained by the presence of different receptive substances in the different tissues, but 

 this view would scarcely explain why, in small doses, atropine exerts a stimulating effect 

 on the respiratory centre, and protocatechyl-tropeine no such stimulant action. Un- 

 fortunately, it is not possible to determine the action of the two constituent groups of 

 these compounds by investigating the products of their hydrolysis. It was early 

 shown by FraserU that tropine and tropic acid produce no atropine-like action, and it 

 was consequently not surprising to find that simple protocatechyl compounds possess no 

 action like that of protocatechyl-tropeine. The substances I investigated were proto- 

 catechyl-aldehyde,|| methyl -protocatechyl-aldehyde (vanillin), and di-methyl-proto- 

 catechyl-aldehyde (piperonal). Intravenous injections of these compounds produced no 

 effect on the respiration resembling that produced by protocatechyl-tropeine. There is 

 thus no evidence leading us to assume that the actions of protocatechyl-tropeine can be 

 attributed with any certainty to the two constituent groupings individually. 



* Arch.f. ezp. Path. u. Pharm., v., p. 463 [1876]. t AnnaUn d. Chemie, Bd. 217, p. 82 [1883]. 



X Trans. Roy. Soc. Edin., xxv., p. 693 [1869]. § Arch. f. exp. Path. u. Pharm., xxxvii., p. 218 [1896]. 



% Proc. Roy. Soc. Edin., 1869, p. 558. 

 || Prepared by acting on piperonal with phosphorus pentachloride. 



