ANGIONEUROTIC EDEMA 279 
All of these particular organs of. internal secretion, 
therefore, seem normally to respond directly to involun- 
tary nerve stimuli and to codperate with the involun- 
tary nervous system in vasomotor control. Vasodila- 
tion occurs under nervous stimulation which bears with 
it no intimation of danger to the body. Concrete exam- 
ples are the emotions of embarrassment and anger. 
Under this type of stimulus the thyroid gland pours 
out its vasodilating secretion into the blood stream in 
increased amount, with the result that mild hyper- 
thyroid symptoms supervene for a time. Vasoconstric- 
tion, on the contrary, occurs in response to nervous 
stimulation, which carries with it definite suggestion of 
danger to the organism. Blood, which might be lost 
were the peripheral circulation to sustain injury while 
relaxed or dilated, is hurried from the surfaces into the 
interior and safer portions of the body. Bodily heat 
necessary to life is thereby conserved. The classic ex- 
ample of this type of stimulus is fright, either conscious 
or unconscious. The chromaffin system and the pos- 
terior lobe of the pituitary under such an impulse in- 
crease their internal secretions and aid in vasoconstric- 
tion. The stimulus of vasoconstriction partakes of the 
nature of a life-conserving measure and will normally 
supercede any involuntary vasodilating stimulus, which 
is not concerned in the conservation of life. 
A logical scheme of norma] vasomotor control, there- 
fore, seems to present itself, i. e., a nervous system for 
instantaneous reaction, with two separate groups of 
glands of internal secretion standing ready immediately 
thereafter to reénforce the reaction required, whether 
it be vasodilation or vasoconstriction. 
This, however, is not all. It is now generally ac- 
cepted that between the various ductless glands there 
exists a reciprocal action. The thyroid, the chromaffin 
tissue, and the posterior lobe of the pituitary all acceler- 
ate the processes of metabolism. In this they are in- 
