134 RESPONSES OF CELLS ON THE BIOLOGICAL LEVEL 



sulphur mustard compounds, activity seems to be asso- 

 ciated v^dth the abihty of the chloride ion to dissociate 

 from the jS-chloroethyl group, leaving a positively charged 

 carbonium ion which has the capacity to react with 

 many cell components. Although many speculations 

 have been put forward about the biochemical mechanism 

 through which these compounds act, the evidence so far 

 available is too sparse to enable any definite conclusion 

 to be drawn. 



It is possible that a useful guide to the mode of action 

 of many mitotic poisons, including the nitrogen mus- 

 tards, will be obtained from cytochemical studies. At 

 present such studies are very few, and so far have been 

 more indicative of the degree of involvement of chemical 

 processes in the biological response itself than of the 

 biochemical mechanism initiating the biological response. 

 For example, some comparative studies have been 

 made of the Feulgen reaction for deoxypentose nucleic 

 acid and of the reaction of Takamatsu and Gomori for 

 alkaline phosphatase. Some of these results are shown 

 in Plate ill (pages 128 and 129). It will be seen that the 

 anomalies produced in the distribution of nucleic acid 

 are strikingly similar to those produced in the distri- 

 bution of phosphatase. 



It must, of course, be remembered that the identifi- 

 cation of the biochemical mode of action of a compound 

 such as nitrogen mustard may prove to be extraordinari- 

 ly difficult by the biochemical techniques which are yet 



