ANGIONEUROTIC EDEMA 279 



All of these particular organs of internal secretion, 

 therefore, seem normally to respond directly to involun- 

 tary nerve stimuli and to cooperate 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 normal 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 reenforce 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- 



