FACTORS ACT ON THE CELLS 129 



subject, which will require careful elucidation if the 

 actual physical laws on which it is based are to be 

 found out, and I venture to think that this method will 

 supply a means by which these laws can be determined ; 

 a large amount of careful experimentation will be 

 necessary, however, with a large variety of substances. 

 The chemical factors, such as alkalies and salts, will 

 have to be tried in greater variety; after which it 

 seems to me probable that one will be able to settle 

 whether the increase and decrease in diffusion which 

 they cause is due to their atomic weight or the osmotic 

 pressure, or what. One point, however, should be 

 clearly appreciated, which is this, that these chemical 

 factors which increase or retard the diffusion of other 

 substances, act not on the substance diffusing into the 

 cell, but on the cell itself. For instance, as will be 

 shown later on, alkalies, by increasing the diffusion 

 of kreatin or xanthin, increase the rapidity of cell- 

 division induced by these extractives. But the alkalies 

 have no effect on either kreatin or xanthin. The way 

 they increase diffusion into the cell is by causing the 

 cell to absorb substances more readily. And so with 

 acids, salts, and other chemical factors. 



Lastly, these simple laws of diffusion must be taken 

 into consideration throughout researches with this 

 method, for no results will be obtained if they are 

 forgotten. The equation has been found to be of 

 more use when stain is employed. Later on, when one 

 is experimenting with single substances and no stain, 

 the arrangement of the jellies is more simple, and the 

 equation is not used so much. 



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