Aconitine, Sfc, in relation to their Chemical Constitution. 343 



towards aconitine and diacetylaconitine. In this action, aconine 

 opposes independent rhythm of auricles and ventricles facilitating 

 the transmission of the normal impulse, and it reduces the tendency 

 to delirium of the ventricle. Only lethal doses reduce the activity 

 of cardiac vagus terminations. The vaso-motor centre is practically 

 unaffected. 



The circulation remains active in frogs for days, in entire absence 

 of reflex and respiratory movements. 



Action on Respiration. 



Aconitine at first stimulates the respiratory centre and the sensory 

 vagal fibres in the lung. Depression rapidly follows, death in 

 mammals being due to central respiratory failure. The peripheral 

 innervation of respiratory muscles is not interfered with. 



Diacetylaconitine produces a slighter initial stimulation than aconi- 

 tine. Death results from central failure. Pulmonary oedema is 

 commonly observed in rabbits. Respiratory spasm occurs at death. 



Benzaconine does not appear to stimulate either respiratory centres 

 or pulmonary vagus as do the two former. The centres are depressed 

 from tli e first ; respiratoryfailure induces death without spasm ; to 

 this the reduced action of motor nerve endings in respiratory muscles 

 contributes. 



Aconine, whilst slowing the respiration from its action upon the 

 centres, possesses a pronounced curare-like action upon motor nerve 

 endings in respiratory muscles. No spasm attends death. 



Action on the Nervous System. 



Aconitine in large doses causes occasional loss of consciousness, 

 with failure of conjunctival reflex and dilated pupil. This is not a 

 directly narcotic effect, but is secondary to reduced oxidising po wer of 

 the blood from circulatory and respiratory impairment. For a time 

 there is evidence of stimulation of motor areas, and especially of the 

 medulla with its contained centres ; to this depression succeeds ; reflex 

 centres in the cord are stimulated, and then depressed by large doses. 

 In frogs, voluntary movement outlasts reflex. Sensory nerves at the 

 periphery are depressed in function after very trausitory stimulation, 

 whilst motor nerves are practically unaffected. 



Diacetylaconitine produces a stimulation of the medulla, but less 

 in degree than that caused by aconitine. The subsequent depression, 

 especially of the respiratory centre, is well marked, the respiration 

 being relatively more affected than the circulation. The general 

 reflex function of the cord is depressed after preliminary excitement. 

 The action with reference to sensory nerves is the same as that of 



