THE MECHANISM OF LIFE 511 



nucleated pieces, appears, the former perishing, while the latter re- 

 generate themselves into complete individuals. 



The behaviour of non-nucleated pieces of cells may, therefore, be 

 summarised in the statement, that, after the passage of a stage of 

 excitation caused by the stimulation of the operation, every piece 

 continues to carry out the movements peculiar to it in the uninjured 

 organism and to react to stimuli in the same manner as before the 

 operation. The normal character of the movements is not changed 

 until the appearance of the phenomena of necrobiosis, which affect 

 the non-nucleated protoplasm and lead to death. 



It appears in all such experiments that, after the passage of a 

 stage of excitation caused by the operation, the movements of non- 

 nucleated pieces of protoplasm continue for a long time, frequently 

 for several days, completely unchanged ; they undergo disturbances 

 only in the course of the necrobiosis of the piece and finally cease. 

 The facts discovered by Hofer agree completely with this. If, how- 

 ever, the normal movement of the protoplasm continues for days 

 after the removal of the nucleus, the nucleus cannot be a regulat- 

 ing centre for the movement, and thus the theory falls. 



2. Nucleus and Protoplasm as Links in the Metabolic Chain of 



the Cell 



It appears from the above discussion that the later views 

 upon the dominance of the nucleus in the cell, in whatever form 

 they are presented, are as little justified as the earlier ideas, which 

 recognised the protoplasm alone as the essential bearer of life. 

 Everything suggests that the truth lies between the two, i.e., that 

 neither the nucleus nor the protoplasm alone plays the chief role 

 in the life of the cell, but that the two are concerned equally in 

 the inauguration of vital phenomena. 



All the experiments and observations so far upon the relations 

 of the nucleus and the protoplasm show that this view is the 

 correct one. It would lead too far to present all the facts bearing 

 upon this question ; only the more important ones will here be 

 noticed. 



The first and most significant one is the phenomenon, already 

 mentioned and confirmed by all past vivisection-experiments upon 

 a great variety of cells, that after a longer or shorter time non- 

 nucleated protoplasmic masses invariably perish, just as do nuclei 

 deprived of protoplasm. Unquestionable proof is thus afforded 

 that the vital phenomena of the cell come about only through the 

 undisturbed correlation of the two parts of the cell. That this cor- 

 relation is a metabolic correlation is a priori evident, since vital 

 phenomena are merely the expression of cell-metabolism. But 

 this fact is proved by special facts relative to phenomena that 

 occur up to the time of death in protoplasmic masses deprived of 



