266 CLASSICS OF MODERN SCIENCE 

 the state of the matter : the material of which the cells are composed is 

 capable of producing chemical changes in the substance with which it 

 is in contact, just as the well-known preparation of platinum converts 

 alcohol into acetic acid. This power is possessed by every part of the 

 cell. Now, if the cytoblastema be so changed by a cell already formed, 

 that a substance is produced which cannot become attached to that cell, 

 it immediately crystallizes as the central nucleous of a new cell. And 

 then this converts the cytoblastema in the same manner. A portion of 

 that which is converted may remain in the cystoblastema in solution, or 

 may crystallize as the commencement of new cells; another portion, 

 the cell-substance, crystallizes around the central corpuscle. The cell- 

 substance is either soluble in the cytoblastema, and crystalHzes from 

 it, so soon as the latter becomes saturated with it; or else it is in- 

 soluble, and crystallizes at the time of its formation, according to the 

 laws of crystallization of bodies capable of imbibition mentioned above, 

 forming in this manner one or more layers around the central cor- 

 puscle, and so on. If we conceive the above to represent the mode of 

 formation of cells, we regard the plastic power of the cells as identical 

 with the power by which crystals grow. According to the foregoing 

 description of the crystallization of bodies capable of imbibition, the 

 most important plastic phenomena of the cells are certainly satisfac- 

 torily explained. But let us see if this comparison agrees with all the 

 characteristics of the plastic power of the cells. 



The attractive power of the cells does not always operate symmet- 

 rically ; the deposition of new molecules may be more vigorous in par- 

 ticular spots, and thus produce a change in the form of the cell. This 

 is quite analogous to what happens in crystals ; for although in them 

 an angle is never altered, there may be much more material deposited 

 on some surfaces than on others ; and thus, for instance, a quadrilateral 

 prism may be formed out of a cube. In this case new layers are de- 

 posited on one, or on two opposite sides of a cube. Now, if one layer 

 in cells represent a number of layers in a common crystal, it may be 

 easily perceived that instead of several new layers being formed on 

 two opposite surfaces of a cell, the one layer would grow more at those 

 spots, and thus a round cell would be elongated into a fibre ; and so 

 with the other changes of form. Division of the cells can have no 

 analogue in common crystals, because that which is once deposited 

 is incapable of any further change. But this phenomenon may be 



