390 



PROFESSOR C. 11. MARSHALL ON THE 



refractory periods, and which in all probability is to be associated with the combined 

 effects of increased irritability and paralysis previously described. 



Boehm,* and Hober and Waldenberg,! record some observations on the action 

 of tetra-ethyl-ammonium chloride on the isolated frog's muscle. Boehm also found 

 that it did not produce tonic contracture, and he indicates that it has no influence on 

 the direct irritability of the muscle. The graphs of Hober and Waldenberg, on the 

 other hand, appear to show a greater degree of toxicity than was obtained by Boehm 

 or myself. 



Action on Motor Nerve Endings of Mammals. — Both increased excitability and 

 paralysis of the motor nerve endings are seen in mammals as in frogs. It has been 

 shown in an earlier part of this paper that, in rabbits, the intravenous injection of 

 large doses of tetra-ethyl-ammonium chloride causes paralysis and rapid death, and 



Fig. 2. — Effect of continuous indirect stimulation of frog's gastrocnemius after fourteen minutes' immersion 

 in 1'5 per cent, pure tetra-ethyl-ammonium chloride. Secondary coil at 27 cm. Primary current 

 from single accumulator cell. Contractions enlarged five times. Time marking ten seconds. 



that minimal doses induce slight and transient dyspnoea. By injecting these minimal 

 doses into the veins of an anaesthetised animal during continued stimulation of a 

 motor nerve, a depressant action on the nerve-endings can be demonstrated. The 

 effect produced by the minimal dose (O'Ol g. per kg. body-weight) inducing symptoms 

 is, however, very slight; a fall in the height of the contraction commencing about 

 fifteen seconds after the beginning of the injection and reaching about one-third the 

 extent of the contraction in one minute occurs, but complete paralysis is not 

 produced. Paralysis to this mode of stimulation is only obtained with a dose of 

 0"02 g. per kg. body-weight. When such a dose is injected into the external jugular 

 vein, complete paralysis to continued electrical stimulation of a nerve of the fore 

 limb is produced in fifteen to twenty seconds (fig. 3). The effect, however, is very 

 transient. A few seconds after stopping the stimulation the nerve is again irritable, 

 and it quickly becomes more irritable than before ; but, as in the case of other 

 substances paralysing motor nerve endings, rapid exhaustion follows continued 



* hoc. cit. t Loc. cit., p. 344. 



