PERMEABILITY OF SURFACE LAYER OF CELLS. 2O/ 



through the now permeable plasma-membrane. According to 

 Lyon's 1 observations the carbon dioxide production by the divid- 

 ing e gg exhibits a rhythmical increase and decrease running 

 parallel with the rhythm of cell-division ; the periods of increased 

 carbon dioxide production probably correspond to periods of in- 

 creased permeability. 



Such changes ought, on the membrane theory, to be accom- 

 panied by changes in the state of electrical surface polarization. 

 Experimental proof of the existence of such changes is difficult 

 but probably not altogether impracticable. Miss Hyde has 

 attempted- - using the capillary electrometer, with one electrode 

 on the blastodisc of dividing fundulus eggs, the other on the 

 opposite pole, to determine if, during cell division, any potential 

 difference makes its appearance between the dividing portion of 

 the egg and its unaltered general surface. 2 While her results are 

 not altogether unequivocal, they do seem to indicate that at or 

 about the time of cleavage the outer surface of the blastodisc 

 becomes negative relatively to the general outer surface of the 

 egg i. e., undergoes a change of potential similar to that which 

 occurs during stimulation, indicating increased permeability. 

 These important and interesting experiments should be repeated 

 and confirmed. There are in fact various indications that during 

 cell -division the potential difference between the exterior and 

 interior of the cell undergoes marked alteration. The disposi- 

 tion of the colloidal material of the cell at this time in the char- 

 acteristic radiations is strong confirmatory evidence ; this phe- 

 nomenon plainly suggests the polarization of colloidal particles in 

 a strong electrical field. It is a corollary of the above theory 

 that with the appearance of an increased permeability imply- 

 ing depolarization of the surface layer the peripheral regions of 

 the protoplasm must become for a time at least, until the poten- 

 tials are equalized positive relatively to the interior. If the 

 voltage of the surface potential change is comparable to that of 

 the action-current of muscle, i. c., ca. 0.05-0.08 volt (as is highly 

 probable), a potential gradient of considerable steepness will exist 

 temporarily, at the time of increased permeability, between the 



1 E. P. Lyon, American Journal of Physiology, 1904, XL, p. 52. 



2 I. H. Hyde, ibid., 1904, XII., p. 241. 



