384 On the Action of Ammonia and its Salts, Sfc. [June 16, 



under maximal, whilst a disturbance of the relationship of auricular 

 and ventricular contractions may be induced. 



(c.) The area of the heart to which stimulation is applied. — A refrac- 

 tory period demonstrable under stimulation of the ventricle may cease 

 to occur when the sinus venosus is the seat of irritation. 



(d.) The action of heat, cold, and drugs. — Thus cold prolongs the 

 systole^ the refractory period, and the latency of an induced contrac- 

 tion ; whilst strychnia, leaving the curve of systole unaltered, lengthens 

 the refractory period to a marked degree. 



VII. " On the Action of Ammonia and its Salts, and of Hydro- 

 cyanic Acid upon Muscle and Nerve." By T. Lauder 

 Brunton, M.D., F.R.S., and Theodore Cash, M.D. Re- 

 ceived May 26, 1881. 



(Abstract.) 



Ammonia. — The curve caused by stimulating either muscle or nerve 

 is prolonged. Fatigue increases this prolongation much more rapidly 

 than it would do in the case of a healthy muscle. The viscosity, 

 or residual contraction, remaining after active contraction is much 

 more increased in the case of direct (muscle) than of indirect (nerve) 

 stimulation. 



Chloride of Ammonium. — A powerful, though slightly lengthened, 

 contraction occurs on direct stimulation. The muscle, as stimulated 

 from the nerve, yields a few (if any) lengthened and feeble contractions, 

 and then ceases to respond altogether to stimulation. 



Nitrate of Ammonium. — The nerve, in this case, is not more affected 

 by the poison than the muscle. If the poisoning be very complete, 

 neither direct nor indirect stimulation has any effect ; if it is not so, 

 the curve is observed to be prolonged. In the case of both, but 

 especially in that of the directly stimulated muscle, the contraction 

 remaining after stimulation is very extensive. 



Nitrite of Ammonium. — If poisoning be complete, no reaction occurs 

 either on direct or indirect stimulation ; if not, the curves of both are 

 much prolonged, even more so than in the case of the nitrate. The 

 rapid repetition of stimulation causes the curve to become enormously 

 prolonged, whilst the viscosity after the active contraction is much 

 increased. 



Cyanide of Ammonium. — Stimulation of the nerve produces no 

 effect whatever; whilst that of the muscle causes a considerable 

 though prolonged curve. Viscosity is much increased. The curve of 

 hydrocyanic acid alone, yielded by both direct and indirect stimulation, 

 is prolonged, but it neither shows the length nor the viscosity of the 



