THEORY OF THE CELLS. 209 



The following may be conceived to be 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 nucleolus of a new cell. And then this con- 

 verts the cytoblastema in the same manner. A portion of that 

 which is converted may remain in the cytoblastema in solution, 

 or may crvstallize as the commencement of new cells : another 

 portion, the cell-substance, crystallizes around the central cor- 

 puscle. The cell- substance is either soluble in the cytoblastema, 

 and crystallizes from it, so soon as the latter becomes saturated 

 with it ; or else it is insoluble, 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 corpuscle, and so on. 

 If we conceive the above to represent the mode of the 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 satisfactorily explained. But let us see if this 

 comparison agrees with all the characteristics of the plastic 

 power of the cells. (See above, p. 19 A et seq.) 



The attractive power of the cells does not always operate 

 symmetrically; the deposition of new molecules may be more 

 vigorous in particular 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, then- 

 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 deposited 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 elou- 



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