74 IMBIBITION AND MOLECULAR STRUCTURE 



various fluids is in all essential points similar to that occurring in water. 

 Hence the fact that cell-walls do not swell in alcohol or carbon bisulphide 

 merely shows that the attraction existing between the substance of the 

 cell-wall and either fluid, i. e. the force of imbibition, is not strong enough 

 to overcome the resistance to separation offered by the component molecules, 

 or micellae. There is no need for a special explanation of the fact that the 

 amount of swelling in a watery solution is different from what it is in 

 pure water, nor why water and salts are absorbed from a solution in 

 different proportion to that existing in the solution in question, for if the 

 affinity for water is the more marked it is only natural that a correspond- 

 ingly larger relative amount of water should be absorbed. For example, 

 when dried bladders are placed in a saturated solution of Glaubers salts, 

 the absorption of water causes crystals to be deposited from the solution 1 . 

 It is not, however, always the water which is most actively absorbed, as 

 is shown by the absorption of dyes, salts, &c. by coagulated egg-albumin 

 or charcoal. Similarly indiarubber absorbs, from a mixture of water and 

 alcohol, only the alcohol, and thus reduces the alcoholic percentage of the 

 mixture. In all such cases the concentration of the watery solution imbibed 

 will alter as the amount absorbed increases, and as the particles of the 

 imbibing substance separate more widely from one another. If the attrac- 

 tion for water is relatively very great, the water imbibed may be either 

 pure or in the form of an extremely dilute solution. Indeed, the water and 

 salts of a saline solution may actually be separated by filtration through 

 semi-permeable membranes capable of imbibition. These phenomena are 

 of the highest physiological importance, for the diosmotic exchanges of 

 the cell are determined and regulated by the power of absorbing water 

 and dissolved substances possessed by the cell and its membranes. 



The molecular movements and changes brought about by imbibition 

 must necessarily have important bearings upon the chemical and other 

 processes taking place in organized bodies. In a state of very fine sub- 

 division the sum total of the surface-tensions of the component particles 

 of a substance is very great, and becomes of decisive importance. Thus 

 charcoal or spongy platinum are, in virtue of the enormous amount of 

 surface exposed, capable of marked absorption or of inducing various 

 chemical reactions, while in the diamond or in a piece of solid platinum 

 these powers are reduced almost to vanishing point. Indeed the pheno- 

 mena of absorption are on the borderland between chemistry and physics, 

 and apparently are the direct results of the same properties and forces which 

 determine the consistency and rigidity of solid bodies. The close study 

 of the phenomena of absorption and surface-tension is of value in many 



1 Ludwig, Zeitschr. f. rationelle Medicin, von Henle u. Ffeufer, 1849, Bd. vm, p. 15 ; Pfeffcr, 

 Osmot. Unters., 1877, p. 40. 



