I40 PROTOPLASMIC ACTION AND NERVOUS ACTION 



tion, while ingenious, does not seem sufficient; in muscle 

 and other living cells immersed in anisotonic solutions 

 water seems to pass with equal readiness in either direc- 

 tion through the membrane; for example, Arhacia eggs 

 in hyper- and hypotonic sea water shrink and swell 

 (respectively) at about the same rates/ Hober refers 

 the difference observed by Bernstein to the greater 

 turgor of the living cells ;^ this explanation also seems 

 doubtful, since turgor is either absent or slight in verte- 

 brate tissues. The simplest as well as most probable 

 explanation is that the permeabiUty to water increases 

 with death, along with the permeability to other sub- 

 stances. As the plasma membrane loses its semi- 

 permeability, w^ith the associated fineness of texture, it 

 also loses its relative impermeability to water. 



Permeability to water is one of the little studied 

 properties of cells. Yet it is an important property 

 which appears to be constant for a particular cell under 

 definite conditions. There is evidence that it varies 

 with the physiological state and activity of the cell, 

 and in certain cases, especially in gland cells, the indica- 

 tions are that it is under nervous control. Thus when 

 the chorda t^onpani is stimulated, the submaxillary gland 

 secretes a copious watery saliva; similarly the sweat- 

 glands and the kidney secrete actively under certain 

 conditions, but not under others. In most cases the 

 secretory substances leave the cell in aqueous solution; 

 and although the factors are complex, there seems to 

 be little doubt that the transport of the secretion across 

 the cell-boundary is associated with an increased permea- 



' R. S, Lillie, American Journal of Physiology, XLV (1918), 406. 

 * Hober, op. cit., p. 255. 



