ANGIONEUROTIC EDEMA 285 



scratching and rubbing, and with this fatigue the per- 

 meability of the wall increases with resultant limited 

 serum oozing, i. e., wheal formation. 



In simple urticarias this wheal formation is of short 

 duration. With no marked vasoconstricting impulse 

 ensuing, tonus gradually returns to the fatigued vaso- 

 dilators, increased vessel wall permeability disappears, 

 exuded serum is taken up by the normal processes of 

 tissue drainage, and the wheal fades. It is unlikely that 

 local deposits of toxins and osmosis thereto enter into 

 the creation of such lesions, since disappearance of the 

 wheal follows so promptly upon the cessation of exter- 

 nal irritation. 



Here then it would seem that hyperthyroid action 

 plus local vasodilator fatigue are the direct cause of 

 simple urticarial lesions. 



Between the short-lived manifestations of simple 

 urticaria and the long-lived lesions of angioneurotic 

 edema there appear to be differences only as to the ex- 

 citing cause and the duration of the individual swell- 

 ings. In the angioneurotic type nervous stress or 

 fatigue seem to be the predominating features in the 

 etiology. We know these factors, absent in simple 

 urticatria, cause profound adrenal irritation, rather 

 than thyroid stimulation. Adrenal excitation, however, 

 always entails thyroid stimulation, so that in angioneu- 

 rotic types thyroid stimulation is present. Further- 

 more, in profound nervous excitation or fatigue, diges- 

 tion often is curtailed or temporarily stopped, and pro- 

 teins, whose digestion is interfered with, may be assimi- 

 lated later in forms particularly irritating to the 

 organism, and capable of producing as components 

 of the blood any or all the phenomena ascribed to 

 foreign proteins in the blood, including both thy- 

 roid and adrenal irritation. Except in cases of se- 

 vere nervous reaction a temporary hyperthyroid secre- 

 tion either occurs first or quickly supervenes after 



