THE NUCLEUS 59 



enucleate pieces may move, respire, and respond to certain stimuli — 

 activities which depend upon catabolic processes; but they do not undergo 

 regeneration, growth through the formation of new albuminous material, 

 or division — activities which involve organic synthesis. 



Among the many reactions involved in metabolism the most impor- 

 tant, according to modern physiology, is oxidation, for the energy utilized 

 by the organism is derived immediately from the union of protoplasm or 

 of its inclusions with oxygen. A relation between the nucleus and oxida- 

 tion and reduction has therefore been sought. 



Following the experiments of Spitzer (1897), who observed that 

 nucleo-proteins extracted from certain animal tissues have the same 

 oxidizing power as the tissues themselves, it was suggested by Loeb 

 (1899) that the nucleus is the center of oxidation in the cell. Loeb 

 pointed out that this would explain the inability of enucleated cell- 

 fragments to undergo regeneration. This conclusion was supported by 

 R. S. Lillie (1903, 1913), who showed that rapid oxidation occurs both 

 at the surface of the cell and at the surface of the nucleus. Osterhout 

 (1917) found that "injury produces in the leaf-cells of the Indian Pipe 

 (Monotropa uniflora) a darkening which is due to oxidation. The oxida- 

 tion is much more rapid in the nucleus than in the cytoplasm and the 

 facts indicate that this is also the case with the oxidation of the uninjured 

 cell." Other investigators^^ have opposed the oxidation theory. Fur- 

 ther evidence in its support is brought forward by Chambers (1923a). 

 In healthy cells (amoebae, ciliated cells, echinoderm eggs) Janus green 

 does not enter the nucleus, but as the cells become moribund the dye 

 enters and colors the reticulum red. This probably means that the nor- 

 mal resistance to the penetration of the dye is lost, whereupon the reduc- 

 ing ability of the nucleus becomes manifest in the change of Janus green to 

 diethylsafranin. This reducing power is lost at death. 



In interpreting the results of such experiments, particularly those 

 in which the cell is enucleated by mechanical means, it has not always 

 been sufficiently borne in mind that some of the effects upon metabolism 

 may be due to the injury itself rather than to any sort of normal activity 

 in the parts which remain. It is therefore very difficult to obtain by 

 such direct means unequivocal evidence regarding the precise manner in 

 which the nucleus functions during the normal life of the cell. Even 

 when the results of enucleation seem clearly to indicate a dependence 

 of certain functions on the nucleus, they do not limit to the nucleus 

 the performance of those functions. Removal of the cytoplasm would 

 also cause a cessation of such activities. Each function, though it 

 may be peculiarly subject to the differential influence of some one 

 organ, is, in reality, an act of the protoplasmic system as a whole. The 

 nucleus may be said "to control" an activity only in the sense that 



s^Lynch (1919) on Amoeba, Wherry (1913), W. Schiiltze (1913), Reed (1915). 



