IV] AND STRUCTURE OF THE CELL 321 



And, in thus moving towards the pole, it will do so, as appears 

 actually to be the case in the dividing cell, along the course of the 

 outer hues of force, the so-called "mantle-fibres" of the histologist*. 



Such considerations as these give general results, easily open to 

 modification in detail by a change of any of the arbitrary postulates 

 which have been made for the sake of simpHcity. Doubtless there 

 are other assumptions which would meet the case; for instance, 

 that during the active phase of the chromatin molecule (when it de- 

 composes and sets free nucleic acid) it carries a charge opposite to 

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

 would accordingly move towards different poles under the influetice 

 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 demonstrate, by such illustrations 

 as these, that, whatever be the actual and as yet unknown modus 

 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 f." 



While it can scarcely be too often repeated that our enquiry is 

 not directed towards the solution of physiological problems, save 

 only in so far as they are inseparable from the problems presented 

 by the visible configurations of form and structure, and while we 

 try, as far as possible, to evade, the difficult question of what 



* • We have not taken account in the above paragraphs of the obvious fact that 

 the supposed symmetrical field of force is distorted by the presence in it of the 

 more or less permeable bodies; nor is it necessary for us to do so, for to that 

 distorted field the above argument continues to apply, word for word. 



t Michael Foster, Lectures on the History of Physiology, 1901, p. 62. 



