1901.] Properties of the Arterial and Venous Walls. 



115 



skeletal muscle, it (or the ammonium salt) causes speedy and complete 

 relaxation of the contracted arterial muscle (fig. 1). This relaxing 

 effect is much more powerful and rapid than that which follows im- 

 mersion in saline solutions, such as ammonium chloride (13 per cent.);, 

 which dissolve out the muscle-proteid, and the mode of action seems 

 to be different, for the ; sulphocyanide solution seems to extract very 

 little proteid from the arterial wall when it has acted sufficiently long 



Fig. 1. 



to cause complete relaxation ; on the other hand, sulphocyanide causes 

 precipitation of proteid in a saline extract of the arterial wall. In 

 contrast with this, saline fluids like the ammonium chloride solution 

 extract a large amount of proteid before they effect complete relaxa- 

 tion, and many hours are necessary for the completion of the effect 

 (e.g., 24 hours). Magnesium sulphate solutions (5 per cent.) require 

 days. v , ; 9 ,- ff M >^, 



When relaxed by sulphocyanide the artery shows a permanent loss 

 of excitability and contractility. , 



Ammonia Vapour. — A contracted artery exposed to strong ammonia 

 vapour (in the same way as described in the case of chloroform vapour) 

 speedily begins to relax • in a very few minutes the change is well 



