NATURAL RESISTANCE AND FATIGUE 149 



stomach might be accounted for by postulating the 

 development of an increased resistance of the mucosal 

 cells to the action of mustard. While such a concept 

 would suffice to explain the development of an in- 

 creased tolerance towards the introduction of mustard 

 into the stomach, it would in no manner account for 

 the development of a generalized resistance towards 

 mustard, as evidenced by the experiments with the 

 plasters. Consequently, we must seek further for an 

 adequate explanation of the facts. 



If it be accepted, as appears reasonable, that the 

 mustard liberates cytost from the cells of the gastric 

 mucosa, we may develop an hypothesis along the fol- 

 lowing lines. Let us assume first that the vesicant ac- 

 tion of mustard when applied locally to a given tissue 

 takes place in the following manner. At the site of 

 contact the mustard injures a number of tissue cells 

 which in turn liberate cytost. The latter, upon dif- 

 fusing to the underlying cells, subjects them to its 

 action, and so on. Eventually the capillaries are 

 reached, and, as has been shown previously, their per- 

 meability is increased by the action of cytost. Because 

 of this increased permeability, there is an exosmosis 

 of fluid into the surrounding tissues, and bleb forma- 

 tion takes place. Now it is to be noted that in this 

 chain of events the factor leading to vesication is the 

 peripheral liberation of cytost and its subsequent ac- 

 tion upon the underlying tissues and capillaries. 



Since divers chemical substances can behave as vesi- 

 cants, it would appear that in general their actions are 

 similar to that postulated above for mustard. Indeed, 

 that vesication of the skin is due to a product liberated 

 by the tissue cells themselves is shown by the beautiful 



