CYTOCHEMICAL ASPECTS 3 



above are considered, it becomes at once clear that the 

 physico-chemical structure of the cell is in a dynamic 

 condition. The fact that the broad outlines of structure, 

 as shown by classical histological methods, are not read- 

 ily changed, is indicative of certain stable elements 

 amongst those determining cell behaviour. But this 

 should not hide from us the great variation which may 

 occur on the chemical level. This variation occurs at 

 just that level on which we must expect most drugs to 

 act, so that in a sense the variability of the cell at this 

 chemical level is of more importance to us than the 

 relatively static nature of certain structural patterns. 



It is possible to procedure redistributions of most 

 substances in the cell without irreversibly damaging the 

 cell. E.g. when a cell goes into division, the organisation 

 of some of the cell products is totally changed in the 

 production of a spindle. The sharp distinction between 

 nuclear sap and cytoplasmic material breaks down. Al- 

 ternatively, by centrifuging the cell, we can obtain a 

 new distribution of substances quite unlike that which 

 arises in a cell under normal conditions or when it is 

 dividing. If the use of centrifugal force is not excessive, 

 the cell can reconstitute the original organisation of sub- 

 stances, and continue with its normal functions unim- 

 paired. In the case of Ascaris eggs, the unfertilised eggs 

 may be centrifuged at 100,000 times gravity for four 

 days, and yet still develop normally when fertilised. 

 Thus particular adjuxtapositions of matter which are 



-3/x 





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