ON THE RELATION BETWEEN, ETC. 377 



that it is more complicated than the molecular structure of 

 any other cell. We have only to imagine that the meta- 

 bolism in the egg- cell is continually changing, never 

 remaining the same for two consecutive moments, so that 

 each condition causes the following condition and is itself 

 the outcome of the condition last preceding it. Con- 

 sidering how close is the connection between metabolism 

 and change of form, each change in the metabolic exi- 

 gencies of the developing organism must be responded to 

 by a further and more complicated structural change. The 

 assumption of greater complication of the molecular structure 

 of the original egg cell is thus entirely superfluous. 



It may appear as if the idea of molecular structure of 

 living substance is inconsistent with that of the continual 

 flow of matter. We have here, however, on a small scale, 

 the same relation as that existing between change ot form 

 in the oreanism, and metabolism. Metabolism consists 

 in chemical processes. These processes, however, are only 

 brought about because each atom or group of atoms or 

 molecules attracts, by chemical affinity, other atoms, group 

 of atoms or molecules in a certain direction. This causes 

 a continual flow of matter, some atoms or groups of atoms 

 being withdrawn and others taking their places. If these 

 atoms and groups of atoms are always of the same kind, and 

 if their entrance and exit always take place in the same 

 manner and direction, as must be the case so long as the meta- 

 bolism of the whole remains unaltered, a certain ordering of 

 the particles results which we must call structure although 

 the whole substance is in motion, in a continual flow. It is 

 only in this way that, for instance, the phenomena of the 

 regeneration of the cell can be explained. A cell from 

 which a portion has been removed can regain its original 

 form provided that it is capable of producing the reserve 

 matter required for its reconstruction. The reserve matter 

 will reach the injured part through the usual channels, 

 being attracted thither by the remaining particles, etc. 

 Should the injured cell no longer have the power to pro- 

 duce the necessary matter for regeneration, i.e., if the 

 entire metabolism has suffered lasting injury, the recon- 



