104 THE MECHANISM OF ABSORPTION AND TRANSLOCATION 



cellulose was continually reduced. Moreover, molecules of sodium may be 

 transmitted through glass by a process of electrolysis, and it is possible 

 that the weak electric currents circulating in living cells l may under 

 particular conditions, and in virtue of their continuous action, exercise an 

 important influence upon translocatory processes. Moreover, the nature of 

 the plasma is such as to render it possible that a substance may combine 

 chemically with the plasmatic elements, thus being transmitted internally, 

 and then set free again. When vacuoles are emptied non-diosmosing 

 substances clo actually pass through the protoplasm -. 



By these or other means non-diosmosing and even insoluble bodies 

 are transferred by the vital activity of the protoplast through its substance 

 and membranes in either direction. In the case of substances capable of 

 diosmosis a physical transference is all that is necessary, though where 

 a production of diosmosing compounds must first take place this is only 

 possible with the assistance of the living organism. To maintain a con- 

 tinuous supply, the protoplast alters or modifies the diosmosing substances 

 as fast as they are absorbed ; and hence all the different diosmotic processes 

 are originated and correlated by the vital activity of the living organism 3 . 



In general, the direction in which a substance is absorbed is dependent 

 upon the maintenance of a certain potential energy of absorption, and 

 though it is possible to imagine a plasmatic membrane as having the power 

 of temporarily or permanently allowing a substance to diosmose in one 

 direction only, still no such case has as yet been proved to exist 4 . 

 Apparently the nature of the solution with which it is in contact has a distinct 

 influence upon the nature and powers of the plasmatic membrane, and it is 

 thus quite possible that differences arising from such causes may exist 

 between the ectoplasmic and the vacuolar membranes. Localized differ- 

 ences between the different regions of a plasmatic membrane may serve 

 to permit of the escape of a particular substance at a given spot, or to 

 allow a transference to a particular neighbouring cell to be possible. 



The actual final results are not only dependent upon the diosmosis, 

 but are also influenced by all the varied conditions and circumstances 

 which modify and direct diosmosis, or render it possible. From what has 

 been already said, it is at once evident why it should often be extremely 

 difficult to determine all the factors at work in producing a given result. 



1 Haacke, Flora, 1892, p. 455. Walden (Zeitschr. f. physik. Chemie, 1^92, Bd. X, p. 718) has 

 shown that the permeability of a membrane by a compound, and by the ions into which the 

 compound may be resolved, is not the same, as Ostwald ibid., 1890, Bd. vi, p. 69) suggested. 



3 Pfeffer, Vacuolenhaut, 1890, p. 283. 



3 Pfeffer, ibid., 1890, p. 290; Studien zur Energetik, 1892, p. 268. 



* For details see Pfeffer, Plasmahaut u. Vacuolen, 1890, p. 288, and Overton, Uber osmot. 

 Eigenschaften, &c., 1895, p. 26 (Sep.-abdr. a. d. Vierteljahrsschr. d. Naturf.-Ges. in Zurich). In 

 the first-named work it is shown that Janse assumed the existence of permeability in one direction 

 on insufficient grounds. 



