342 Dr. Gash and Prof. Dunstan. Pharmacology of 



and also to the ultimate reduction of ventricular action to incoordi- 

 nate contraction (delirium). 



The vaso-motor centre is at first stimulated, bat later depressed 

 in function, but peripheral splanchnic stimulation is. active to some 

 degree throughout poisoning. 



Diacetylaconihne, whilst producing effects in the main resembling 

 those of aconitine, shows less tendency to cause independent rhythm 

 of ventricles upon auricles. In half the experiments made a failure 

 of systole occurred without asequence, in the remaining half an 

 aconi tine-like effect was witnessed. 



The cardiac vagus is less affected than by aconitine, but the result 

 of its stimulation depends much upon the sequence or non-sequence 

 of ventricular upon auricular action present at the time. 



The vaso-motor centre and peripheral vaso-constrictors respond 

 to this alkaloid much as they do towards aconitine, but stimulation 

 in the early stage of action is less marked. 



Benzaconine. — After very brief pulse acceleration, slowing with 

 reduction of blood pressure occurs, the latter being due mainly to 

 the depression of the motor mechanism within the heart. After a 

 stage of irregularity, during which full diastole of both auricles 

 and ventricles is exceptional, a blocking of auricular impulses to 

 the ventricle succeeds, so that a rhythm of 2 to 1 is produced. 

 (After aconitine this state of affairs is largely reversed.) Complete 

 though transitory failure in the production of a spontaneous beat 

 (the ventricles being first involved, then the auricles) is seen in a 

 large proportion of experiments. This is not due to stimulation of 

 inhibitory apparatus, which is put out of action by atropine, for the 

 phenomenon occurs after atropine. It is referable rather to depression 

 of the motor apparatus. Contraction returns spontaneously, either 

 from spontaneous revival in excitability of this apparatus, or from 

 stimulation of the highly venous blood. 



The vaso-motor centre, though depressed in function, retains some 

 action, until the very low pressure is reached which invariably 

 precedes death. 



Vagus stimulation causes slowing, until in a late stage of poisoning, 

 the blood pressure remaining very low, its action' fails. After 

 effective stimulation, pressure rises beyond the original level from 

 acceleration of the heart and strengthening of the systole. 



Digitaline is the most effective antagonist towards benzaconine. 



Aconine is, relatively to the three compounds just considered, 

 harmless towards the heart. At first it stimulates the vagal roots 

 slightly, causing a slower beat. As, however, it strengthens the 

 systole of the ventricle the blood-pressure rises, and is maintained at 

 a high level throughout a long experiment. Asequence or disorder 

 of rhythm is not produced, but an antagonistic effect is shown 



