IMBIBITION 207 



in the sense of going into solution, or by imbibition, in the sense 

 of soaking it up, as does a jelly or a blotter? The problem is 

 one that emphasizes the vital importance of structural con- 

 tinuity in protoplasm. Sugar, not blotting paper, is miscible in 

 water. Imbibition and solution both depend on the preferential 

 adsorption of water by molecules, but the actual mechanism of 

 the two phenomena appears to differ. The molecules of soluble 

 substances are free when in solution (as is sugar in water) . Those 

 of substances that imbibe water are held together (as in a gelatin 

 block). There is no limit to the amount of water in which a 

 miscible substance (sugar) will diffuse; but a substance (gelatin) 

 that imbibes water and is immiscible in it takes up a definite 

 maximum amount and then stops. Structural continuity holds 

 it together. This is the case with protoplasm; it imbibes water 

 but does not go into solution with it. 



Dujardin, one of the earliest workers on protoplasm, described 

 protoplasm as a living jelly, insoluble in water. Hertwig referred 

 to it as a viscous, water-immiscible substance; and Butschli said 

 the same, viz., that protoplasm is not miscible in water. There 

 are, however, supporters of the opposite opinion. They base 

 their view on the rapid diffusion of water when it is injected into 

 protoplasm. The same would be true if water were injected 

 into a moist, but not saturated, sponge or blotter. There is 

 much evidence to show that protoplasm possesses a continuous 

 framework, comparable to a "brush heap," not fixed or rigid but 

 labile. This framework exhibits great affinity for water but is 

 immiscible in it, just as is true of gelatin. Much of the inorganic 

 and organic matter that permeates the protoplasmic framework 

 is in true aqueous solution. 



Biological Applications. — The manner in which protoplasm 

 takes up water is but one of the many biological applications of 

 imbibition. The following are others. 



Growth, in so far as it involves mere distention, or getting big, 

 and germination, which is a form of growth, are due in part to 

 imbibition. 



Muscle action has been regarded as due to swelling or imbibi- 

 tion, though the evidence for it is not sufficiently convincing. 

 It is said that a bee's wing may vibrate two hundred times a 

 second. Hofmeister believed that protein strands as fine as the 

 fibrils in the muscle of a bee's wing may imbibe water and give 



