THE PHARMACOLOGICAL ACTION OF PROTOCATECHYL-TROPEINE. 283 



chloride, and probably also by the alkaloid pukateine, are due mainly to stimulation of 

 the vagal terminations. According to Iodlbauer,* the effect of tetramethyl-ammonium 

 chloride is less after section of both vagi, and consequently he concludes that its action 

 on the circulation is partly, if not mainly, central. He also obtained a marked rise of 

 blood-pressure when this drug was injected after atropine, a result he attributes to 

 stimulation of the vasomotor centre. I have obtained a rise of blood-pressure on cutting 

 both vagi a few minutes after the injection of tetramethyl-ammonium chloride, but have 

 not observed any difference on the frequency of the heart-beats after injection of this 

 substance whether the vagi were divided or not. After atropine had been given, the 

 usual slowing of the heart did not occur, nor was there any rise of blood-pressure. 



The slowing of the heart's frequency and the fall of blood-pressure produced by the 

 papaverin derivatives investigated by Pohl are attributed by him to the stoppage of 

 the respiration. He does not, however, refer to any investigations bearing on this point 

 in his paper, and he gives no tracings from which the action on the circulation might 

 be inferred. 



The action of protocatechyl-tropeine on the circulation differs from that of most 

 substances producing temporary paralysis of the respiration, in that it paralyses the 

 vagal endings within the heart. Hence the diminution in the frequency of the heart- 

 beats and the fall of blood-pressure are less than are produced by most members of this 

 class of respiratory paralysants. As previously stated, the fall of blood-pressure caused 

 by these tropeines is probably due to a depressant action on the cardiac muscle, an 

 action which in all probability is present in the case of the other substances also. 



From these statements it is evident that no uniformity, such as exists in the case of 

 the respiration, characterises the action of these different substances on the circulation, 

 and this further supports the statement made previously that their action on the two 

 systems is not correlated. 



Remarks on the Relation between Chemical Constitution and 

 Pharmacological Action. 



Protocatechyl-tropeine, as previously stated, was one of a series of tropeines in- 

 vestigated for the purpose of determining the difference between a lactone and the 

 corresponding hydroxy -acid. As it is not a lactone it was used as one of the control 

 substances, and it was found that, unlike pilocarpine and the lactone-tropeines, it does 

 not lose its action when a molecular quantity of caustic alkali is added to its aqueous 

 solutions. Even the addition of distinct excess of caustic alkali and prolonged standing 

 do not influence its pharmacological action to any appreciable degree. It is evident, 

 therefore, that the replacement of the hydrogen of the phenolic hydroxyls by an alkali 

 metal is of no pharmacological importance. 



A point of interest on which the action of protocatechyl-tropeine throws a little 



* Loc. cit. 



