IV] STRUCTURE OF THE CELL 185 



during the active phase of the chromatin molecule (during which 

 it decomposes and sets free nucleic acid) it carries a charge opposite 

 to that which it bears during its resting, or alkaline phase ; and 

 that it would accordingly move towards different poles under the 

 influence of a current, wandering with its negative charge in an 

 alkahne fluid during its acid phase to the anode, and to the kathode 

 during its alkahne phase. A whole field of speculation is opened 

 up when we begin to consider the cell not merely as a polarised 

 electrical field, but also as an electrolytic field, full of wandering 

 ions. Indeed it is high time we reminded ourselves that we have 

 perhaps been deahng too much with ordinary physical analogies : 

 and that our whole field of force within the cell is of an order of 

 magnitude where these grosser analogies may fail to serve us, 

 and might even play us false, or lead us astray. But our sole 

 object meanwhile, as I have said more than once, is to demon- 

 strate, by such illustrations as these, that, whatever be the actual 

 and as yet unknown modiis operandi, there are physical conditions 

 and distributions of force which could produce just such phenomena 

 of movement as we see taking place within the living cell. 

 This, and no more, is precisely what Descartes is said to have 

 claimed for his description of the human body as a " mechanism *." 



The foregoing account is based on the provisional assumption 

 that the phenomena of caryokinesis are analogous to, if not identical 

 with those of a bipolar electrical field; and this comparison, in 

 my opinion, offers without doubt the best available series of 

 analogies. But we must on no account omit to mention the 

 fact that some of Leduc's diffusion-experiments offer very remark- 

 able analogies to the diagrammatic phenomena of caryokinesis, as 

 shewn in the annexed figure f. Here we have two identical (not 

 opposite) poles of osmotic concentration, formed by placing a drop 

 of indian ink in salt water, and then on either side of this central 

 drop, a hypertonic drop of salt solution more lightly coloured. 

 On either side the pigment of the central drop has been drawn 

 towards the focus nearest to it ; but in the middle line, the pigment 



* M. Foster, Lectures on the History of Physiology, 1901, p. 62. 

 t Op. cit. pp. 110 and 91. 



