THEORY OF THE CELLS. 207 



crystallization, but which exist in some other unknown manner 

 between the atoms of solid substance. It is not possible, 

 therefore, to determine whether that part of the crystal which 

 is first formed must have an angular figure or not. 



An ordinary crystal consists of a number of laminae ; when 

 so small as to be but just discernible, it lias the form which 

 the whole crystal afterwards exhibits, at least as far as regards 

 the angles ; we must therefore suppose that the first layer is 

 formed around a very small corpuscle, which is of the same 

 shape as the subsequent crystal. We will call this the pri- 

 mitive corpuscle. It is doubtful what may be the shape of 

 this corpuscle in the crystals which are capable of imbibition. 

 The first layer, then, is formed around the corpuscle in the 

 way mentioned; it grows by intussusception, and thus forms a 

 hollow, round or oval vesicle, to the inner surface of which the 

 primitive corpuscle adheres. As all the new molecules that arc 

 being deposited may be placed in this layer without any altera- 

 tion being required in the law which regulates the coalescence 

 of the molecules during crystallization, we must conclude that 

 it remains the only layer, and becomes greatly expanded, so as 

 to represent all the layers of an ordinary crystal. It is, how- 

 ever, a question whether there may not exist some reasons why 

 several layers can be formed. We can certainly conceive such 

 to be the case. The quantity of the solid substance that must 

 crystallize in a given time, depends upon the concentration of 

 the fluid; the number of molecules that may, in accordance with 

 the law already mentioned, be deposited in the layer in a given 

 time depends upon the quantity of the solution which can 

 penetrate the membrane by imbibition during that time. If 

 in consequence of the concentration of the fluid there must be 

 more precipitated in the time than can penetrate the mem- 

 brane, it can only be deposited as a new layer on the outer 

 surface of the vesicle. When this second layer is formed, tin 1 

 new molecules are deposited in it, and it rapidly becomes ex- 

 panded into a vesicle, on the inner surface of which the first 

 vesicle lies with its primitive corpuscle. The first vesicle now 

 either does not grow at all, or at any rate much more slowly, 

 and then only when the endosmosis into the cavity of the 

 second vesicle proceeds so rapidly that all that might be pre- 

 cipitated while passing through it, is not deposited. The second 



