44 DYNAMICS OF LIVING MATTER 



is the active force, but through the slow but gradual entrance of 

 NaCl into the muscle, and possibly the loss of water and salts, on 

 the part "of the muscle, new conditions for the absorption of water 

 are created which correspond with Van Bemmelen's observations on 

 gels. 



If a little acid be added to a 0.7 per cent solution of NaCl (which 

 is about isosmotic with the gastrocnemius of a frog), the gastrocnemius 

 will absorb considerable quantities of water from such a solution. The 

 quantity of water absorbed increases with the quantity of acid used. 

 For inorganic acids it can be shown that the effect is chiefly determined 

 by the hydrogen-ions, and not by the anions. Organic acids, however, 

 act considerably stronger than should be expected, if the effect were 

 purely due to the free hydrogen-ions.* The cause of this anomaly is 

 not yet known. If, however, acids are added to a hypertonic solution 

 of NaCl, the efifect is the reverse; the acid diminishes the amount of 

 water absorbed by the muscle.f Alkahs increase the absorption of 

 water under all circumstances. In these cases the acids and alkalis 

 act probably through their combination with the proteids, whereby 

 the conditions for the absorption and giving off of water are changed. 

 It is therefore obvious that other forces than the mere osmotic pressure 

 play a r61e in the absorption of liquids by tissues. 



The same seems to be true for the reverse process; namely, 

 the secretion of liquids from the cells. In these cases work is often 

 done against the osmotic potential. It is evident that another force 

 must be at work besides the mere osmotic pressure. The fact discov- 

 ered by MacCallum, that the same salts which increase the peristaltic 

 motion of the intestine also increase the secretory action of the glands 

 of the intestine,J seems to indicate that this force may be of the nature 

 of the contractile forces. The same salts which increase the secretion of 

 liquid from the blood into the intestine also increase the secretory 

 action of the kidneys. 



Hober § has recently called attention to another possibility. Ham- 

 burger had found that acids, e.g. CO^, increased- the permeability of red 

 blood corpuscles for certain anions. Hober has shown that such an 

 increased permeability for anions must lead to a difference of potential 

 between the inner and outer surface of the semipermeable elements, 

 the inner surface assuming a positive charge. It is possible that such 

 differences of potential, in case they lead to an electric current, may 



• Loeb, Pfluger's Archiv, Vol. 69, p. i, 1897 > Vol. 71, p. 457, 1898. 

 t Loeb, Pfiiiger's Archiv, Vol. 75, p. 303, 1899. 



j J. B. MacCallum, University of California Publications, Vol. I, p. 5, 1903; and pp. 

 81 and 125, 1904. Pfluger's Archiv, Vol. 104, 1904. 



§ R. Hober, Pfliiger's Archiv, Vol. 102, p. 196, 1904. 



