THE PHYSIOLOGY OF CELL-DIVISION iz 
ions; this has been definitely and conclusively demonstrated by 
the work of Nernst, Lapicque, Lucas, and Hill; this theory is 
confirmed by the fact that during the stimulated state, when the 
membranes undergo increase in permeability, stimulation becomes 
difficult or impossible (refractory period); i.e., increase in the 
permeability of the plasma-membranes beyond a certain degree 
makes electrical polarization and hence stimulation, impossible ;** 
this, it may be pointed out, is the essential reason why ‘dead’ 
cells are non-irritable. The proofs that stimulation involves 
increase in permeability of the plasma-membrane are too numer- 
ous to detail here ;* electrical changes, as long known, are an inva- 
riable accompaniment of stimulation. All of these facts, with 
many others, indicate that the electrical condition of the boundary 
membranes of cells, i.e., of the semi-permeable plasma-membranes, 
is a matter of fundamental importance to vital processes, and 
that this condition is variable and dependent on the degree of 
ionic permeability of the membranes. 
I have recently brought these facts and considerations to bear 
on the problem of cell-division.*® Since free cells, like egg cells, 
show the same osmotic properties as muscle-cells, it is fair to 
assume that they possess the same electrical properties. Investi- 
gation indicates that this is in fact the case.*® On application 
of the Ostwald-Bernstein theory of the origin of the demarcation- 
current potential to the case of the dividing cell, the familiar 
32 Nernst: Archiv fiir die gesammte Physiologie, 1908, vol. 122, p. 275. La- 
picque: Numerous papers in Comptes rendus de la Société de Biologie and 
Archives de Physiologie normale et pathologique; cf. especially the latter journal, 
1908, vol. 10, p. 601. Lucas: various papers in Journal of Physiology; cf. vol. 36, 
1907, p. 253; vol. 37, 1908, p. 459; vol 39, 1909, p. 461; vol. 40, 1910, p. 225. Hill, 
ibid., vol. 40, 1910, p. 190. 
33 Cf. my paper in the American Journal of Physiology, 1909, vol. 24, pp. 17, 18, 
for a brief discussion of this point. Tait: Quarterly Journal of Experimental 
Physiology, 1910, vol. 3, p. 221, has brought forward evidence indicating that the 
duration of the refractory period is identical with that of the action-current. 
Both phenomena, on the present theory, are manifestations of the same essential 
change, viz., increase in surface-permeability. 
34 T have reviewed this evidence in American Journal of Physiology, 1909, vol. 
24, p. 14, and 1911, vol. 28, p. 197. Cf. also Science, 1909, vol. 30, N.S., p. 245. 
35 Cf. Biological Bulletin, 1909, vol. 17, p. 188. American Journal of Physiology, 
1910, vol. 26, p. 106. 
3 Cf. I. H. Hyde: Amer. Journ. Physiol., 1904, vol. 11, p. 52. 
JOURNAL OF MORPHOLOGY, VOL. 22, NO. 3 
