344 Dr. Cash and Prof. Dnnstan. Pharmacology of 



aconitine, but motor nerve terminations, though they are not power- 

 fully affected, are reduced in activity by diacetylaconitine. 



Benzaconine causes a lethargic and ultimately semi-narcotised con- 

 dition, which is referable to low intracranial blood-pressure as well 

 as to a direct action upon the cortex. Whilst the medullary 

 centres are early depressed, both direct and cross cord reflexes are 

 elicited in a limb excluded by vascular ligature from access of the 

 alkaloid. Sensory nerves are unaffected except in deep poisoning. 

 On the other hand, motor nerves and their terminations are reduced 

 in function, a peculiar intermittency of response following stimula- 

 tion. 



Aconine produces in mammals loss of volition and impairment of 

 conjunctival reflex only shortly before a large dose proves fatal. 

 Motility is interfered with, but this is mainly due to a curare-like 

 effect upon motor nerve endings. The respiratory centre is depressed, 

 respiration failing when the heart still beats vigorously. 



Action on Oxidation Processes. 



All the four alkaloids here considered reduce the oxidising power 

 of vegetable protoplasm ; aconitine being most and aconine least 

 active. Diacetylaconitine is more energetic than benzaconine. 



Action on Internal Temperature. 



Aconitine produces a fall (exceptionally preceded by a slight rise), 

 which increases as respiratory slowing develops, but the minimum 

 is reached (50 — 70' in rabbits) after a partial recovery of respira- 

 tion. Exposure to a cold atmosphere increases the fall and delays 

 the recovery. Diminished oxidation produced directly and through 

 impairment of circulation and respiration indirectly are causal to the 

 fall. 



A dose of aconitine less than half the lethal proportion will cause 

 a fall of nearly 2° C. below the normal. 



Diacetylaconitine occasions less effect than aconitine on the tem- 

 perature when the dose bears an equal relationship to the respective 

 lethal doses. This is due to a less vigorous action on heart and 

 respiration. Like aconitine, it interferes both indirectly and directly 

 with oxidation. 



Benzaconine produces a trifling reduction of temperature until a 

 dose is reached which greatly reduces the pulse and speed of respira- 

 tion when a proportionate fall occurs. The reduction of muscular 

 movement tends still further to limit heat production. Propor- 

 tionately to its toxic dose the effect is not so active as in the case of 

 diacetylaconitine. 



