THEODOR SCHWANN 261 



tides of organic matter, nor interspaces filled with water. The water 

 occupies the infiltrated organic substances, just as it is present in a 

 solution, and there is as much diflference between the capacity for 

 imbibition and capillary perrneation, as there is between a solution and 

 the phenomena of capillary permeation. When water soaks through a 

 layer of glue, we do not imagine it to pass through pores, in the com- 

 mon sense of the term ; and this is just the condition of all substances 

 capable of imbibition. They possess, therefore, a double nature, they 

 have a definite form like solid bodies; but like fluids, on the other 

 hand, they are also permeable by anything held in solution. As a 

 specifically lighter fluid poured on one specifically heavier so carefully 

 as not to mix with it, yet gradually penetrates it, so also, every solu- 

 tion, when brought into contact with a membrane already infiltrated 

 with water, bears the same relations to the membrane, as though it 

 were a solution. And crystallization being the transition from the 

 fluid to the solid state, we may conceive it possible, or even probable, 

 that if bodies, capable of existing in an intermediate state between 

 solid and fluid could be made to crystallize, a considerable difference 

 would be exhibited from the ordinary mode of crystallization. In 

 fact, there is nothing, which we call a crystal, composed of substance 

 capable of imbibition ; and even among organized substances, crystal- 

 lization takes place only in those which are capable of imbibition, as 

 fat, sugar, tartaric acid, &c. The bodies capable of imbibition, there- 

 fore, either do not crystallize at all, or they do so under a form so 

 different from the crystal that they are not recognized as such. 



Let us inquire what would most probably ensue if material capable 

 of imbibition crystallized according to the ordinary laws, what varie- 

 ties from the common crystals would be most likely to show them- 

 selves, assuming only that the solution has permeated through the parts 

 of the crystal already formed, and that new molecules can therefore 

 be deposited between them. The ordinary crystals increase only by 

 apposition ; but there may be an important difference in the mode of 

 this apposition. If the molecules were all deposited symmetrically 

 one upon another, we might indeed have a body of a certain external 

 form like a crystal ; but it would not have the structure of one, it would 

 not consist of layers. The existence of this laminated structure in 

 crystals presupposes a double kind of apposition of their molecules ; 

 for in each layer the newly-deposited molecules coalesce, and become 



