STRUCTURES RESEMBLING ORGANIC GROWTHS. 



in many physiological processes of a movement of fluid through 

 cells, or from one region to another within cells, e. g., the activities 

 of gland-cells which are normally associated with bioelectric 

 currents flowing in the cells tow r ard the secreting surface 1 and 

 the protoplasmic flowing movements in plant-cells. Certain 

 recent observations of Chambers 2 on the micro-dissection of sea- 

 urchin eggs illustrate the readiness with which flowing move- 

 ments may be set up in protoplasm by local injury of the cell- 

 surface, i. e., by conditions which are known in general to render 

 the cell-surface locally negative. The application of a needle 

 to a sea-urchin egg in a hanging drop "produces peculiar curients 

 in the egg-substance. The currents pass directly from the 

 pushing object in a straight line through the egg to the anterior 

 end where they curve outward and flow back along the surface 

 to be caught again in the flow from the pushing object." The 

 region of contact is presumably negative relatively to other 

 regions of the cell-surface, i. e., the positive stream flows outside 

 the cell from the unaltered to the altered part of the surface 

 and thence through the cell; the observed flow of fluid is thus 

 in the direction of the positive stream. The possibility that dis- 

 solved materials may be thus transported from one region of 

 the cell to another ought especially to be noted. If such a 

 condition is general, a flow of fluid in reference to any temporarily 

 altered region of the cell-surface will take place as a result of 

 electrical transport; and this flow may largely determine the 

 supply of material for the repair or reconstitution of the altered 

 area. The fact that in the microscopic precipitation-tubules 

 described in this paper a flow T of fluid, due apparently to electrical 

 transport, actually plays an essential part in the structure- 

 forming process, is highly suggestive in relation to the problem 

 of the conditions of structure-formation in cells. There is also 

 evidence that a centripetal flow of fluid from the polar and 

 extra-equatorial regions of the cell-surface takes place in eggs 



1 Cf. Langley, Schafer's "Textbook of Physiology," Vol. i, p. 517. Unfortu- 

 nately this observation does not in itself indicate whether the electric current is the 

 cause or result of the movement of fluid through the gland. A flow of solution 

 through a porous partition, however caused, gives rise to an electric current. 



2 Chambers, "Microdissection Studies," Amer. Journ. Physiol., 1917, Vol. 43, 

 p. i; cf. p. 7; also Journal of Exper. Zool., 1917. 



