PHARMACOLOGICAL ACTION OF TETRA-ALKYL- AMMONIUM COMPOUNDS. 21 



The effect of stimulation with the secondary coil at 30 cm. is shown in fig. 2, 

 which also shows the action of the same dose of tetra-methyl-ammonium chloride 

 during continuous stimulation of the nerve. The cessation of the contraction seven 

 seconds after the commencement of the injection is striking. The method of con- 

 tinuous stimulation does not, however, show recovery from the effects of the drug 

 owing to fatigue being so easily induced. For this purpose intermittent stimulation 

 is necessary. 



When strong or moderately strong intermittent stimuli are employed, complete 

 paralysis of the nerve-endings may not be observed after the injection of 1 mg. p. kg. 

 body-weight of tetra-methyl-ammonium chloride. Each stimulation after the admini- 



Fig. 3. — Contractions of fore limb of rabbit produced by stimulation of musculo-cutaneous nerve during recovery 

 from tetra-methyl-ammonium chloride. For description see text. 



stration of the drug may produce a well-marked, although less than normal, contraction ; 

 but the contraction is not maintained, and notwithstanding the continuance of the 

 stimulus, quickly falls to or near the abscissa (fig. 3). This contraction, indeed, may 

 be so short as to resemble a simple twitch. This effect of apparent rapid exhaustion was 

 first shown by Boehm * in the case of curarin. 



Occasionally another effect — a staircase effect — is obtained by stimulating a nerve 

 during recovery from the paralysing action of tetra-methyl-ammonium chloride, and 

 this, combined with the rapid exhaustion of the nerve -endings, produces a curious, 

 humped-back form of curve. This is shown in fig. 3. The animal, a rabbit, was 

 anaesthetised with ether; the brain was excised at 10.43, and the anaesthetic discon- 

 tinued at 11.0. The musculo-cutaneous nerve was isolated and divided, and the 



* Arch. f. exp. Path. u. Pharm., xxxv. p. 16 [1894]. 



