THE BIOLOGY OF THE CELL SURFACE 



substance and thereby dismissing the various inclusions 

 suspended in it as necessary constitutents of cytoplasmic 

 structure, we dismiss much of the work done on the chem- 

 istry of the cell as relevant to the chemistry of the cyto- 

 plasm inasmuch as chemical studies have been made so 

 largely en gros — encompassing everything including food- 

 material and effete matter which might be present in each 

 of the thousands of cells which are often necessary for a 

 single chemical determination. The chemistry of the cyto- 

 plasm, from my point of view, would embrace only the 

 chemistry of the inclusion-free ground-substance. Since we 

 do not yet possess such, we can only approximate it by 

 considering that which remains after we have subtracted 

 from what is known of the chemistry of the whole cell that 

 which is known of the chemistry of the nucleus, of the 

 various inclusions and of the cell-membrane. This so little 

 light does not throw its beams far and we remain still much 

 in the dark. Moreover, there is always the obstacle that 

 what we call the chemistry of the whole cell is not that of 

 living protoplasm; the isolation necessary for chemical 

 study may change the cell-constituents. Micro-chemical 

 studies on cell-inclusions are certainly valuable as are those 

 on the inclusion-laden protoplasm. But there is the great- 

 est need for such studies on the ground-substance itself. 



The definition of cytoplasm here given makes mandatory 

 a revaluation also of studies on the physical properties of 

 protoplasm. Here, in order to know what properties inhere 

 in the ground-substance, unless this be studied as such, the 

 known properties of nucleus and cytoplasmic inclusions 

 should be subtracted from those known for the whole cell. 

 It is a curious fact that in that domain of physical chemis- 

 try which by its definition we should expect to encompass 

 the study of the ground-substance workers have laid more 

 stress on the whole cytoplasmic area and neglected the 

 possibility of investigation of the ground-substance which 



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