The Relation of Excised Muscle to Acids, Salts, and Bases. 287 



general these substances affect the osmotic pressure of gelatine solutions in 

 the same manner as they do the rate of swelling of solid gelatine plates 

 immersed in water. 



" (3) Addition of salts depresses the osmotic pressure of both colloids ; the 

 degree of depression is a function of the nature of both the anion and cation 

 of the salt. It increases in the order, alkali metals < alkali earths (for 

 cations) and CI > plurivalent anions, phosphates (for anions)." 



Muscular Swelling Interpreted as an Osmotic Phenomenon. 



I have quoted direct from Lillie's paper because it makes the phenomena 

 of the relations of excised muscles to acids, salts, and bases appear in a clear 

 light. Evidently, acids and bases raise the osmotic pressure of the muscle 

 colloids, and so water flows in ; salts depress this osmotic pressure and so less 

 water passes into the muscle. Bechhold (3) and others have stated that 

 sugar does not antagonise the swelling of muscles under the action of acids 

 and bases ; and this again falls into line with 'Lillie's work. 



The mechanism by which this osmotic change is brought about follows from 

 Hardy's work on colloidal solutions : acids combine with the colloids in 

 solution to give ionisable complexes which dissociate in such a way that the 

 large colloidal " pseudion " carries a positive charge, and increasing the 

 hydrogen ion increases the degree of dispersity of the colloid particles, and 

 so raises the osmotic pressure of the system (5, 6, etc.). The same holds 

 for the colloids charged negatively by the hydroxyl ion, i.e. for colloidal 

 anions. In the presence of neutral salts, the ionisation of the colloid 

 particles of the muscle is suppressed, they lose their charge and are 

 coagulated. This again recalls the salt globulins, which show no movement 

 in an electric field and are brought out of solution by simple dilution. This 

 view harmonises with Proctor's in ascribing to ionisation the controlling 

 factor in the production of the internal osmotic pressure. It differs in 

 considering that the colloidal ions exert a definite quantum to the final 

 result, greater or less according to their degree of dispersity. 



It has already been recorded in a previous paper that in hypertonic neutral 

 solutions, the loss in weight of an excised muscle is a linear function of the 

 time, and it was suggested that " the linear form of the curve would imply 

 that the loss is due to a change in the state of the muscle, for if it were 

 merely the establishment of an osmotic balance with a fixed effective mass of 

 solute within the muscle the rate would diminish as the effective concen- 

 tration within the muscle approached that outside it." This suggestion that 

 the distribution of the common solvent water between the muscle and the 

 external medium depends partly on the direct osmotic pressure of solutes in 



