The Relation of Excised Muscle to Acids, Salts, and, Bases. 285 



Eemoved to an acid-water system, the increase of the hydrogen ion con- 

 centration and the removal of the salts both act together to increase swelling. 



In a neutral system there are several possibilities. In distilled water, and 

 in hypotonic solutions of sugar, there is an initial swelling of the muscle, 

 due partly to its transference to a medium of lower osmotic pressure and 

 partly to the absence of the normally occurring salts (see further below). 

 In isotonic sodium chloride or Einger solution the muscle remains for a 

 time of constant weight. The special case of the other neutral salts in 

 isotonic solution will also be considered below. In hypertonic neutral 

 solutions the muscle loses weight from the start. All neutral solutions, 

 however, have this in common, that, sooner or later, a muscle immersed in 

 any one of them becomes coagulated and loses weight, regardless of the 

 tonicity of the solution. This must be due to the loss of all free acid in the 

 muscle by diffusion outwards and to the fact that the iso-electric point of 

 the muscle colloids lies near the neutral point, i.e. if it is assumed, as has 

 been done throughout this paper, that the iso-electric point coincides with 

 the point of most complete coagulation, and that the degree of coagulation 

 is measured by the amount of synreresis. 



In an alkali-water system the muscle also shows an initial swelling just 

 as in a neutral hypotonic system. But besides water, hydroxyl ions diffuse 

 into the muscle, and so, the acid in the muscle is neutralised. At this point 

 coagulation of the colloid particles and shortening of the fibres occur simul- 

 taneously, but, as more hydroxyl ions diffuse into the muscle, the system 

 becomes negatively charged, and swelling again sets in (see the curves in 

 fig. A). 



No attempt will be made in this paper to discuss at any length the 

 meaning of the initial swelling in isotonic solutions of potassium, lithium, 

 and ammonium salts. This swelling, under the influence of these salts, can be 

 prevented by injuring the muscle by freezing and thawing (Siebeck, 23), or 

 by saturating the solution used by chloroform. It is therefore possibly con- 

 nected with the state of the muscle as a living system. Hardy has already 

 brought forward evidence to show that, in living blood, the proteins are 

 present as a single large complex (7, Appendix II), which breaks down under 

 adverse circumstances (such as dialysis), setting free the globulin. Possibly, 

 therefore, in living muscle, these same large complex molecules exist, and the 

 first action of the toxic electrolytes is to cause their breakdown, with an 

 accompanying rise in the osmotic pressure. The coagulating effect of the 

 neutral salts follows later, and is the same in general character as that found 

 in non-living colloid systems, i.e. it is a function of the valency of the 

 coagulating ion. 



