ANGIONEUROTIC EDEMA 215 
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 vasoconstricting 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, 
