176 THE PHENOMENON OF 



I have prefaced with these few indications of the 

 structure of the cell, in order to give a preliminary 

 characterisation of the essential parts, the behaviour of 

 which will be of importance to us in the phenomena of 

 Rejuvenescence of the cell. 



II. DESTRUCTION {Entbildung) OF THE CELL. 



"The question of the multiplication of cells includes," 

 says Schleiden,* " the origin and the Hfe of the entire 

 plant." With better right may we say that the examina- 

 tion of the Rejuvenescence of the cell includes that of the 

 whole life of the plant ; for there are plants which run 

 through their entire vegetative vital development in one 

 single cell, consequently without multiplication, but not 

 without partial Rejuvenescence of the cell. The multi- 

 plication of cells itself is nothing else than a phenomenon 

 of Rejuvenescence of the cell. All Rejuvenescences in 

 cell- life, however, are connected with a more or less 

 deeply invading destruction of the already consolidated 

 parts of the cell standing in opposition to a progressive 

 development. These phenomena of undoing and stripping 

 off the proper earlier structures of the cell, are what 

 we have here to examine first of all, and this, first 

 in reference to the coats, then in reference to the con- 

 tents of the cell. 



The cell-membrane, by its hardening and lamellar thick- 

 ening, soouer or later becomes an obstacle to the growth 

 and the vital development of the cell or its successors, 

 the daughter-cells forming within the mother-cell mem- 

 brane. Numerous cells attain the aim of their life with 

 the complete formation of the cell-wall, as, for example, 

 all liber- and wood-cells, the spiral vessels, &c. In other 

 cells, on the contrary, we see the living process overcome 

 the straitening case, sometimes through mechanical 



* ' Grundzugo,' i, 304 (2le Aufg.) 'Principles,' p. 102. 



