ACTION OF VESICANTS 91 



and Dixon have shown that the alkyl fluorophosphonates 

 act upon choUne esterase in a relatively irreversible 

 manner and are also myotics. It thus seems likely that 

 all substances which can produce a sufficient degree of 

 inhibition of choline esterase have myotic activity. 



Table xviii is taken from the work of Dixon and 

 Needham. It shows the action of vesicants on hexokinase 

 in the presence of M/150 glucose. It will be seen that the 

 substances having vesicant activity all poison hexokinase 

 under these conditions, whereas those substances having 

 no vesicant activity are not good poisons for hexokinase. 

 The conclusion appears that all substances inhibiting 

 hexokinase are likely to be vesicant. 



From evidence of the type just given it seems likely 

 that substances having a selective action upon a particu- 

 lar enzyme system are likely to display the same physio- 

 logical activity. 



The Mode of Action of Vesicants 



• 



As was noted in the previous section, the action of vesi- 

 cants upon enzyme systems has been the subject of 

 intensive study, both in England and in America. We 

 shall examine these studies in a little more detail to show 

 the great difficulty which is encountered in reaching a 

 final conclusion as to the actual mode of action of any 

 particular vesicant. We shall particularly consider lewi- 

 site and mustard gas, since these two substances have 



