278 



Miss D. J. Lloyd. 



greater concentrations than 0'005 normal the swelling diminishes with 

 increasing concentration. This is shown in fig. 1. 



4-OO-r 



Fig. 1. 



Abscissce = acidity and alkalinity expressed as fractions of normal. 

 Ordinates = final weights expressed in percentages of initial weights. 

 The continuous line curve is for acid or alkali in distilled water, the dotted curve is for 

 acid or alkali in Ringer's solution. 



In the alkaline solution used (caustic soda) the maximum swelling is also 

 at - 005 normal. This corresponds to a hydrogen ion concentration 

 C H = 10 -11-7 {i.e. 10 -11-7 grm. hydrogen ion in 1 litre of solution). The degree 

 of swelling in alkali is not so great as for the corresponding acid. The curve 

 of swelling in alkali falls sharply both above and below the concentration 

 O'OOo normal, as is also shown in the same figure. 



The Behaviour near the Neutral Point. 



Fig. 1 is a graphical representation of the swelling of muscle in acid or 

 alkali of varying strength. The percentage increase over the original weight 

 is plotted as the ordinate, and the normality of the solution used as the 

 abscissa. It can be seen from the figure that the greatest changes in the 

 degree of swelling occur over a very narrow limit of concentration. 



The point of minimal swelling is drawn, in fig. 1, at the point of absolute 

 neutrality for the external medium. Both to the right and left of this point 

 the curve rises very rapidly. In fact, by using the " normality " of the 

 medium as the abscissa to the curve, and the degree of swelling as the ordinate 

 (as has been done in fig. 1), it can be seen, merely by studying the form of 

 the curve, that very minute changes in the concentration of the hydrogen ion 

 present in the external medium must correspond to large changes in the 



