527 



Acineta tuberosa : A Study on the Action of Surface Tension in 

 Determining the Distribution of Salts in Living Matter. 



By A. B. Macallum, Ph.D., Sc.D., LL.D., F.R.S., Professor of Bio-chemistry 

 in the University of Toronto. 



(Eeceived February 19 —Read May 29, 1913.) 



[Plates 14 and 15.] 



CONTENTS. 



PAGE 



I. Introduction : The General Effects of the Action of Surface Tension 527 



II. The Material and Methods of Investigation 535 



III. The Results 536 



IV. General Observations 542 



V. Summary of Results and General Observations 547 



VI. Literature 548 



VII. Explanation of Plates 549 



I. Introduction : The General Effects of the Action of Surface Tension. 



The distribution of salts in living matter is supposed, in the current 

 conception of the subject, to be on the whole the same as in ordinary fluids. 

 Living matter is generally regarded as a semi-fluid, semi-viscid material in 

 which the conditions, though not fully typical of those which obtain in a 

 fluid like water, are, nevertheless, such as to allow the substances that are 

 dissolved in it to be distributed uniformly throughout it. The only obstacle 

 to this distribution may be presented by a membrane such, for example, as 

 that which encloses or surrounds the cell nucleus. Elsewhere throughout 

 the cytoplasm there is, it is believed, a free play of the force that determines 

 the diffusion of the substance or substances dissolved, until iiniformity in 

 their dispersion obtains throughout the volume occupied by the cytoplasm. 



This force is that postulated in the van 't Hoff theory of solutions extended 

 to include the Arrhenius theory of dissociation. In this composite theory, 

 as is well known, the material dissolved in a fluid is supposed to be in a 

 state analogous to that of a gas, that is, in as rarefied a condition as if its 

 molecules were isolated from each other and occupying alone the volume 

 filled by the solution itself. The molecules of the solute and their ions, 

 when they are dissociated, are thus supposed to be in translational motion, 

 and the resulting pressure — the osmotic pressure — which they give, acts on 

 the surfaces enclosing the fluid as the molecules of a typical gas act on the 

 walls confining it. At every point in the system there would be, on this 



vol. lxxxvi. — b. 2 II 



