THE ACTION OF NEUTRAL SALTS 111 



to a flood of speculations concerning the nature of physiological 

 and pathological processes. These speculations were, unfortu- 

 nately, rarely supported by adequate experimntes and when experi- 

 ments were made the hydrogen ion concentrations were ignored, 

 so that the basis of these speculations is always uncertain if not 

 positively wrong. Thus it has been suggested that muscular 

 contraction is due to swelling caused by acid formation. This 

 may or may not turn out to be correct, but the production of 

 acid in the muscle can only lead to increased swelling if the pH 

 inside the muscle is lower (but not much lower) than that of the 

 isoelectric point of the proteins responsible for the alleged swell- 

 ing; since otherwise the acid formation could only diminish the 

 swelling already existing in the resting muscle. It is obvious 

 that we must know the isoelectric points of the proteins in the 

 muscle, as well as the pH in the resting and the active muscle, 

 before a discussion of the hypothesis becomes profitable. 



It has been stated that edema is due to the swelling of proteins 

 inside the cells caused by acid formation. Not only have none 

 of the measurements of the hydrogen ion concentrations required 

 for such a hypothesis been made but all critical experiments and 

 clinical observations indicate that edema is a phenomenon 

 dependent on increased filtration of liquid from the capillaries 

 into the spaces between tissues or cells; while there is no indica- 

 tion that edema is connected with colloidal swelling. 1 



It has been suggested that the absorption of water by the 

 striped muscle (and by other cells) in hypotonic solutions is due 

 to a colloidal swelling caused by acid formation inside the cells, 

 but it can be shown that if the solution is rendered isotonic by 

 the addition of a sugar, the living muscle no longer absorbs 

 water. 2 This proves that the absorption of water by living 

 muscles (and other living cells) in hypotonic solution is due to 

 the fact that these tissues or cells are surrounded by semiper- 

 meable membranes and that the absorption of water by living 

 striped muscles or cells in hypotonic solutions has no connection 

 with colloidal swelling. 



1 See HIRSCHFELDER, A. D., Trans. Section Pharmacol. and Therapeutics, 

 Am. Med. Assoc., p. 182, 1917; and MOORE, A. R., Am. J. Physiol, vol. 37, 

 p. 220, 1915. 



2 HOBER, R., " Physikalische Chemie der Zelle und der Gewebe," p. 386, 

 Leipsic and Berlin, 1914. LOEB, J., Science, vol. 37, p. 427, 1913. 



