534 SECTIONAL TRANSACTIONS.—I. 
physical conditions conducive to human comfort. Hill’s observations are 
not confirmed ; in well-controlled experiments with eighty-five subjects 
no evidence whatever is found of ‘ nose-opening ’ rays. 
Nose-closing is found to occur not only with a dull fire but also with a 
bright fire. It can also be produced by heating the subject by convection 
(heated air) or by conduction (warm fomentation). Even the sun is a 
potent nose-closer. 
The average person tolerates most heating effects without discomfort and 
without recourse to mouth-breathing ; it is only in those who are peculiarly 
sensitive (e.g. by reason of deflected septa) that any difficulty arises. 
Monday, September 11. 
Discussion on The chemical control of the circulation (10.0) :— 
Sir H. H. Date, C.B.E., Sec.R.S. 
The study of the chemical control of the circulation began with the dis- 
covery of adrenaline and of the pituitary pressor principle. The former is 
predominantly augmentor to vascular tone, though there is evidence that 
its actions include a vasodilator effect; concerning the physiological 
significance of the pituitary principle little is known. 
It has long been improbable that there is any organ of internal secretion 
which forms a hormone predominantly vasodilator in function, though 
depressor substances were early found in most tissues. The first of these 
vasodilator substances to be identified was choline. This was followed by 
histamine which has been shown to exert a dilator effect on the minute 
vessels, complicated to different extents in different species by a constrictor 
action on larger arterioles and venules ; this substance plays an important 
part in the effects of local injury to the skin. Another dilator substance, 
an unstable choline ester and indistinguishable from acetyl choline, is 
liberated as the result of stimulating various parasympathetic nerves and 
the arteriodilator branches of sensory fibres. Further vasodilator sub- 
stances which have been discovered in recent years are the adenosine series, 
constituents of muscle extracts, and kallikrein, which appears to circulate 
in an inactive form in the blood and to be rendered active by a rise of acidity. 
Evidence seems still to be lacking for the direct action of any of these 
vasodilator substances as a true hormone. In this respect there is a general 
contrast between them and the true, mainly vasoconstrictor, hormones ; 
this contrast, however, is by no means an absolute one, since it appears 
possible that adrenaline may be held in an inactive form peripherally, to be 
released by sympathetic nerve-impulses as a humoral transmitter of their 
effects, 
Prof. J. H. Burn. 
It has previously been shown that vasoconstrictor substances such as 
tyramine and ephedrine exert only a slight effect when injected into the 
arterial system of the body wall and limbs of cats or dogs perfused by 
defibrinated blood ; similarly stimulation of the sympathetic chain exerts 
only a slight effect. "The constrictor action of tyramine, ephedrine, and of 
sympathetic stimulation is increased if adrenaline is continually added to the 
blood used for perfusion so as to maintain a uniform concentration. The 
addition of adrenaline has the further effect of bringing to light dilator effécts 
following the injection of ephedrine and the stimulation of the sympathetic 
