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The Action of the Venom of Sepedon heemachates of South Africa. 



By Sir Thomas E. Fraser, M.D., LL.D., Sc.D., F.R.S., Professor of Materia 

 Medica, University of Edinburgh; and James A. Gunn, M.A., B.Sc, 

 M.D., Assistant in the Materia Medica Department, University of 

 Edinburgh. 



(Received June 30, 1908,— Read January 28, 1909.) 

 (From the Pharmacology Laboratory of the University of Edinburgh.) 



(Abstract.) 



The venom used was an extract from the dried venom glands of the 

 Sepedon kcemaehatcs. Its minimum lethal dose by subcutaneous injection per 

 kilogramme was found to be: for the frog, - 0012 gramme; for the rabbit, 

 0001 gramme ; for the rat, - 0016 gramme ; for the cat, - 015 gramme ; for 

 the pigeon, - 0033 gramme ; and, by intravenous injection, for the rabbit, 

 0*00055 gramme. 



In the case of all these animals, the venom primarily and with greatest 

 intensity affects the respiration. Respiratory paralysis is the cause of death 

 in mammals and in birds ; in frogs, the respiratory movements are early 

 paralysed, but death occurs after several days from gradual failure of the 

 circulation. Other conspicuous effects produced by lethal doses in mammals 

 are drowsiness, ataxia, impairment of reflexes, and fall of temperature. In 

 frogs, the venom produces diminution of reflex excitability, motor paralysis, 

 and progressive increase in weight due to oedema. 



In warm-blooded animals, the venom has a marked enfeebling action on 

 the brain and spinal cord, which is only slightly, if at all, produced on the 

 motor nerve ends. In frogs, however, motor paralysis is due to a paralysing 

 action both on the central nervous system and on the motor nerve ends, the 

 former action being characteristic especially of large doses, the latter being 

 more pronounced in the late stages of poisoning with smaller doses. 



The venom has, comparatively with its action on nerve structures, a very 

 slight action on skeletal muscle. 



From the point of view of lethality, the effects of the venom on the circula- 

 tion are of minor importance compared with those on the respiration. Perfused 

 through the frog's heart, strong solutions of Sepedon venom bring about an 

 increase of the rate, followed by arrest of the heart in systole ; and weaker 

 solutions slow the heart and arrest it in diastole. The latter effect is the only 

 one manifested after injection of even 10 times the minimum lethal dose. 



