ANGIONEUROTIC EDEMA 275 



teid circulating in the general blood stream and 

 whose effects, therefore, must be general can mani- 

 fest itself in localized wheals and edemas, unless it be 

 that such areas in some manner previously have be- 

 come peculiarly susceptible to vasoconstric'ting stimuli, 

 and have needed only the stimulation or irritation 

 afforded by a circulating foreign protein to cause them 

 to develop the urticarial phenomena. 



If this be true, what can be the cause of such a pe- 

 culiarly localized susceptibility? Certainly no disorder 

 of an entire nervous system; nor does it satisfy the 

 mind to say that transitory excesses of the vasocon- 

 stricting internal secretions of the adrenal medulla and 

 the posterior lobe of the hypophysis are responsible 

 for these products, like the anaphylaxis producing 

 foreign proteins, are blood-borne and general in their 

 effect, On the contrary, a particular localized sus- 

 ceptibility toward vasoconstricting stimuli must exist 

 before any circulating general vasoconstricting agent 

 can cause localized, circumscribed areas of vasocon- 

 striction. A definite departure from normal vasomotor 

 control is, therefore, plainly present in every area in- 

 volved by the urticarial-like eruption. 



THE MECHANISM OF VASOMOTOR CONTROL 



A review of the mechanism of normal vasomotor 

 control will be of assistance in making clear the possi- 

 bilities which lie in a departure therefrom. There is 

 ample evidence on hand to warrant the belief that 

 every nonstriated muscle fibre and every organ of the 

 body has a double nerve supply from the involuntary 

 system. Irritation or stimulation of one branch of 

 this system produces relaxation of the nonstriated 

 muscle fibres and dilation of the peripheral blood ves- 

 sels (peripheral vasodilation), with a resultant de- 

 creased blood pressure ; stimulation of the other branch 

 causes contraction of the nonstriated muscle fibres, 



