2 12 SOME PROBLEMS OF CELL-ORGANIZATION 



elusion to the view that the centrosome, too, is such an independent 

 organism and that the cell is a symbiotic association of at least three 

 dissimilar living beings ! Such a conception would, however, as I 

 believe, be in the highest degree misleading, even if with Watase we 

 limit it to the nucleus and the cytoplasm. The facts point rather to 

 the conclusion that all cell-organs arise as differentiated areas in the 

 common structural basis of the cell, and that their morphological 

 character is the outward expression of localized and specific forms of 

 metabolic activity. 



It is certain that some of the cell-organs are the seat of specific 

 chemical changes. Chromatin (nuclein) is formed only in the nucleus. 

 The various forms of plastids have specific metabolic powers, giving 

 rise to chlorophyll, to pigment, or to starch, according to their nature. 

 The centrosome, as Butschli, Strasburger, and Heidenhain have in- 

 sisted, possesses a specific chemical character to which its remarkable 

 effect on the cytoplasm must be due.^ Even in regions of the cyto- 

 plasm not differentiated into distinct cell-organs the metabolic activities 

 may show specific and constant localization, as shown by the deposit 

 of zymogen-granules, the secretion of membranes, the formation of 

 muscle-fibres, and a multitude of related facts. Physiologically, 

 therefore, no line of demarcation can be drawn between permanent 

 cell-organs, transient cell-organs, and areas of the cell-substance that 

 are physiologically specialized but not yet morphologically differen- 

 tiated into organs. When we turn to the structural relations of cell- 

 organs, we find, I think, reason to accept the same conclusion in a 

 morphological sense. The subject may best be approached by a 

 consideration of the structural basis of the cell and the morphologi- 

 cal relations between nucleus and cytoplasm. 



B. Structural Basis of the Cell 



It has been pointed out in Chapter I. that the ultimate structural 

 basis of the cell is still an open question ; for there is no general 

 agreement as to the configuration of the protoplasmic network, and 

 we do not yet know whether the fibrillar or the alveolar structure is 

 the more fundamental. This question is, however, of minor impor- 

 tance as compared with the microsome-problem, which is, I think, the 

 most fundamental question of cell-morphology, and which is equally 

 pressing whatever view we may hold regarding the configuration of 



the network. 



Are the granules described as " microsomes " accidental and non- 

 essential bodies, produced, it may be, by the coagulating effects of 



1 Cf. p. 77. 



