ANGIONEUROTIC EDEMA 277 
ous vasoconstricting apparatus—a relationship simi- 
lar in kind to that existing between the vasodilating 
apparatus of the involuntary nervous system and the 
thyroid, but a relationship devoted to a purpose dia- 
metrically opposed—namely, reenforced vasoconstric- 
tion. 
Of the two functions, vasodilation and vasoconstric- 
tion, the former is produced most easily. That it suc- 
cumbs most readily under repeated or severe stimulus 
unless supported by an adequate rise in thyroid con- 
tent of the blood, would seem most likely from the 
natural sequence of events occurring in abnormal as 
well as normal subjects. Patients with a complete ab- 
sence of the thyroid show no tendency to blushing or 
peripheral vasodilation, but on the contrary, are in a 
state of marked chronic peripheral vasoconstriction. 
These patients possess an involuntary nervous mech- 
anism inactivated by reason of the absence of the thy- 
roid principle. Mild hypothyroidism shows but little 
tendency to peripheral vasodilation under nervous 
stimulation, a constant vasoconstriction of more or 
less marked degree existing instead; whereas hyper- 
thyroidism shows a constant vasodilation varying in 
degree with the grade of hyperthyroidism. 
[I cannot refrain from remarking here that in 
hypothyroidism, and especially in the more decided 
types as myxedéme fruste, or myxedema, there is al- 
ways a mechanical factor involved as a result of the 
mechanical puffing of the cells, the so-called infiltra- 
tion first emphasized by Hertoghe. To my mind, the 
local circulatory findings mentioned by the essayist 
are more mechanical in character than functional or 
nervous—the cells are dilated and (myx-)edematous 
and, consequently, the intercellular capillary circula- 
tion is almost impossible—H. R. H.] 
The thyroid gland being supplied by nerve filaments 
from the involuntary system in common with all other 
