THE BIOLOGY OF THE CELL SURFACE 



Undoubtedly, Altmann's granules are mitochondria; as 

 such they are only cell-inclusions. As to other granules 

 described in this connection, one must remember that many 

 granules in cells are purely secretory — that is, precursors of 

 the cell's secretion, as the granules found in a salivary gland 

 or in the pancreas — that some others are storage-stuffs, 

 others, excretory products. In other words, granules are 

 derivatives of cytoplasmic substances or expressions of 

 cytoplasmic activity. That to which they owe their origin 

 and not they themselves would seem more likely to be basic. 



For the reasons given, I think that we may discard the 

 alveolar, filar and granular theories of cytoplasmic struc- 

 ture. Oil-drops, yolk-spheres, threads and granules in the 

 cytoplasm make the contents of a cell a gross suspension. 

 Such a suspension as that of an egg of Nereis or of a sea- 

 urchin does not represent the basic structure of life and 

 its peculiar physical state does not offer any clue to the 

 solution of the problem of vital activity. 



Turning to the menstruum containing the formed bodies, 

 the ground-substance, we find, as stated above, that it 

 appears to be almost optically empty. If, however, one 

 examines the hyaline region of a centrifuged egg of Arbacia, 

 Nereis or Chaetopterus, with extreme care without pressure 

 on the egg — for pressure induces abnormal formations — one 

 can observe very fine granules as barely visible points. 

 Thus, as also said above, the ground-substance is to be 

 considered as a colloidal solution, for it has particles below 

 the size seen under the ordinary microscope, but which can 

 be seen under dark-field illumination. Until we know more 

 of the physics and chemistry of the ground-substance, we 

 must derive a conception of its structure by observing it in 

 the living state and when properly fixed. The fact that 

 well-fixed ground-substance so closely resembles the living 

 makes fixation a supplementary aid in its investigation and 

 permits us to draw conclusions concerning the living state 



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