OF THE INCREASE OF CELLS. 75 



into c. Can anything be more unlike cliemical and 

 physical change ? Neither a, nor 5, nor c can be 

 made by the chemist ; nor if you give him h can he 

 make a or c out of it ; nor can he tell you anything 

 about the " molecular condition " or chemical com- 

 position of «, for the instant he commences his analysis 

 a has ceased to be a, and he is merely deahng with 

 products resiilting from the death of a, not with the 

 actual living a itself. ISTo wonder then that chemists 

 and physicists persist in ignoring a. 



114. Of ttae increase of Cells. — Sevei'al distinct modes 

 of cell increase or multiplication have been described, 

 but in all cases the process depends upon the bioplasm 

 only. It is this which divides : and it is the only 

 part of the cell which is actively concerned in the 

 process of multiplication. It may divide into two or 

 more equal portions, or give oflF many buds or offsets, 

 each of which may grow as a separate body as soon 

 as it is detached. 



The formed material of the cell is perfectly passive 

 in the process of increase and multiplication. Even 

 the apparently very active contractile tissue ot 

 muscle has no capacity of increase or formation. If 

 soft or diffluent, a portion of the formed material 

 may collect around each of the masses into which 

 the bioplasm has divided, but it does not grow in or 

 move in and form a partition, as has often been 

 stated, § 175. When a septum or partition exists, it re- 

 sults not from " growing in," but it is simply produced 

 by a portion of the bioplasm undergoing conversion 

 into formed material of which the partition is composed. 



115. Cuticle or Epidermis. — The most external 

 texture of the body, the cuticle or epidermis, is com- 

 posed entirely of cells or elementary parts, some of 

 which are being constantly removed from the free 

 surface, while new ones gTow up from below. In 

 the cavity of the mouth, on the tongue, and lining 

 the fauces, epithelium wiU be found, which, although 



