I7O RALPH S. LILLIE. 



Another remarkable feature of these precipitation-tubules, al- 

 ready described, is that their formation is associated with a 

 centrifugal flow of fluid along the tubule. This is not surprising 

 when it is considered that they originate by a process of elec- 

 trolysis at local electrical circuits. The passage of an electrical 

 current through a porous diaphragm or other system of capillary 

 tubes has long been known to involve a flow of the solution 

 through the tubes; this is the phenomenon of fluid-transport 

 by the current known as electrical endosmose. The possibility 

 that this process plays a part in the transport of fluid through 

 cells, e. g., in secretion, has at times been touched upon by 

 physiologists; 1 but in the absence of positive evidence it has 

 been for the most part disregarded. Nevertheless it seems 

 certain that currents of fluid must accompany the passage of 

 electrical currents through or between cells, and also that the 

 flow must be in general in the direction of the positive stream. 

 Living protoplasm is a polyphasic system, largely fluid in its 

 consistency, and pervaded by solid structural elements (mem- 

 branes, fibrils, etc.) composed of colloidal material (protein,, 

 lipoid) which is charged negatively in contact with neutral or 

 slightly alkaline media, such as those forming the tissue-fluids 

 and the fluid part of protoplasm. The fluid layers in contact 

 with such structures will accordingly be positively charged ; and 

 displacement of this fluid in the direction of the positive stream 

 is inevitable if the protoplasm forms part of an electrical circuit. 

 Protoplasm always contains salts and is a good conductor of 

 electricity, and its enclosing membranes are readily permeable 

 to water; hence the conditions for such a flow are present. 

 Accordingly we should expect the passage of currents, bioelectric 

 and other, through cells to be associated with a flow of fluid. 

 Apart from such a priori considerations, there is ample evidence 



in the state of electrical surface-polarization is general in living cells, and that 

 the activity of cilia contractile prolongations of the cell-surface is one index of 

 this condition. Any free cell-surface having intermittent polarization might 

 thus give rise to cilia. 



1 Cf. Engelmann, Pfliiger's Archiv, 1872, Vol. 6, p. 97; Waymouth Reid, Phil- 

 osophical Transactions, 1900, Ser. B, Vol. 192, p. 239; Hober, Pfliiger's Archiv, 

 1904, Vol. 101, p. 607. Experiments showing transport of water through tissues 

 (muscle and nerve) by the constant current in the direction of the positive stream are 

 described by Hermann, Pfliiger's Archiv, 1897, Vol. 67, p. 240. 



