SECTIONAL TRANSACTIONS.—I. 535 
chain. It is shown that the effect of a maintained concentration of adrena- 
line on the tyramine response is exerted pari passu with its effect on the 
histamine response, and also with a similar effect on the response to acetyl- 
choline. The vasodilator effect of small doses of adrenaline is not seen in 
circumstances in which vasodilatation from sympathetic stimulation occurs. 
The effect of adrenaline is considered to be an effect on the vessel walls in 
general and not on the neighbourhood of the sympathetic terminations in 
the walls. 
Dr. A. N. Drury. 
Adenylic acid, isolated from muscle, has a depressor activity which is 
shared by related compounds such as adenosine, yeast adenylic acid, and 
yeast cytidylic acid. The last substance is of interest, as there is evidence 
that in muscle extracts a depressor substance is present, in addition to 
adenylic acid, which has very similar properties to yeast cytidylic acid. 
The depressor activity of adenylic acid and adenosine is lost when the 
amino group is split off, and this led to the idea that the effect is associated 
with deamination, though recent work fails to give it support. Adenylic 
acid has been isolated from the blood, and is considered to be the substance 
responsible for the ‘ primary toxicity’ of fresh defibrinated blood. It is 
liberated from damaged muscle and may therefore play a part in the dilata- 
tion of vessels which accompanies injury. Moreover it produces a local 
dilation and leucocytosis, and may be responsible for this phenomenon of 
tissue damage. It is quickly inactivated by the tissues, so that it must be 
liberated continually if it is to produce a lasting effect. 
Dr. J. H. GappuM. 
There are at least two vasodilator substances in some tissue extracts which 
have hitherto baffled the chemists. ‘These have been arbitrarily called 
kallikrein and P-substance. They are both unstable substances with rather 
large molecules, and are both readily carried down from solutions by various 
adsorbents. Both substances produce a fall of blood pressure in animals 
which have received atropine, and so been rendered insensitive to choline. 
They are both distinguished from histamine by the facts that they are 
unstable in acid solutions and produce a fall of blood pressure in etherised 
rabbits. They are distinguished from adenosine by the fact that they are 
unstable in alkaline solutions. 
Kallikrein has been obtained from urine and blood, but has been found 
to be present in a particularly high concentration in the pancreas. It is 
insoluble in alcohol. 
P-substance is present in intestine and brain. It is distinguished from 
kallikrein by its distribution, and by the fact that it is soluble in absolute 
alcohol. ‘There are also various pharmacological differences, but it will be 
difficult to obtain any certain knowledge of the general actions and signi- 
ficance of these substances until better methods of purification can be 
devised than those at present available. 
Dr. W. FELDBERG. 
Prof, R. J.S. McDowa_t. 
When 5 per cent. carbon dioxide is administered to a chloralised cat 
there may be no alteration of blood pressure, but it is not, therefore, to be 
