The Relation of Excised Muscle to Acids, Salts, and Bases. 289 



quarter of an hour after they cease to respond to an electric stimulus. As 

 the curves show no break at any moment which might be considered as the 

 death point, it seems justifiable to assume that the osmotic nature of the 

 exchange of water between a muscle and its surrounding medium, which has 

 been shown to depend (1) on the osmotic pressure of the muscle colloids as 

 determined by their state of configuration, (2) on the osmotic pressure of the 

 crystalloids in the external medium, applies equally well to living as to dead 

 muscles. 



One point of interest arises in this paper with regard to the living muscle : 

 the working muscle is a positively charged system with a hydrogen ion 

 concentration P H < 5. (This follows from the fact that muscles lose weight 

 slightly in a solution with P H = 5.) The iso-electric point for muscles is 

 between P H = 5 and P n == 7. The reaction of normal blood is P H = 7"35 

 (Walpole). There must, therefore, be an electric potential between the 

 muscles and the body fluids, and since the muscle substance is freely 

 permeable to both hydrogen and hydroxyl ions, it seems possible that one of 

 the results of cell oxidation is that by the constant production of carbonic 

 acid in the muscle, this potential is continually maintained. 



Summary. 



1. Acids and alkalies both cause swelling in excised muscle. The degree 

 of swelling is not directly proportional to the concentration of acid or alkali 

 in the surrounding fluid but has a maximum at O005 normal for hydrochloric 

 acid and for caustic soda. Alkalies first coagulate and then redissolve the 

 muscle substance. 



2. The chlorides of the alkali and alkaline earth metals all ultimately 

 coagulate the protoplasm of an excised muscle in isotonic solutions. The 

 bivalent cations show this effect much more rapidly than the monovalent. 

 Distilled water and sugar solutions also coagulate excised muscles. 



3. The iso-electric point for muscle is between P H = 5 and P] t = 7. 



4 It is suggested that the swelling and shrinking of muscles both in the 

 body and out is an osmotic phenomenon, and that the configuration of the 

 colloids of the muscle substance is the chief determining factor which fixes the 

 degree of swelling. Lillie's demonstration that acids and alkalies raise the 

 osmotic pressure of gelatine, while the neutral salts lower it, is in harmony 

 with this view. 



5. The osmotic phenomena of muscle can be fully explained without 

 assuming the presence of a semi-permeable membrane round the muscle 

 fibres. 



