INTRA VENO US INJECTION OF SUPRARENAL EXTRA CT. 955 
a plethysmograph or oncometer, the instrument indicates a great 
diminution in volume of the organ, which can only be accounted for by a 
contraction of its arterioles. 1 This contraction is produced by the direct 
action of the drug upon the muscular tissue of the smaller arteries, and 
not indirectly through the vasomotor centre; for it obtains in the mammal 
equally well" with the spinal cord cut Or the bulb destroyed (Fig. 90), or 
even in the case of the arm after the brachial plexus has been severed 
(Fig. 91). In the frog it is produced also with the brain and spinal cord 
completely destroyed, when salt solution containing suprarenal extract is 
allowed to flow through the arteries. Under these circumstances the 
How of fluid, which, without the suprarenal extract, may have been com- 
paratively rapid, becomes almost completely stopped, and this can only 
be due to the direct action of the extractive substance upon the muscular 
tissue of the smaller arteries. 
The enormous rise of blood pressure which is got after the vagi have 
been cut, is shown in the tracings (Figs. 89 and 90) : the pressure may rise 
to four or five times its original height. Hardly any other agent will 
produce such an enormous increase of pressure, except direct stimulation 
of the vasomotor centre. It is not the case, however, that the elevation 
of blood pressure, and the contraction of the arteries, is due to the 
stimulation of the vasomotor centre by the drug, as was supposed by 
Cybulski and Szymonowicz, for, as we have seen, the action is essentially 
a peripheral one. As shown by Oliver,- it will occur if the extract be 
directly applied to the vessels of the mesentery, either during life or 
in the " surviving " condition. 
The effect of intravenous injection upon the blood pressure passes off in the 
course of a few minutes. After a dose, no matter whether small or large, has 
been injected into a vein, and has produced the results which we have 
recorded, the blood vessels slowly resume their ordinary calibre, the augmenta- 
tion and increased frequency of the heart's beats become gradually lessened, 
and the blood pressure recovers its normal condition. Whilst the pressure is 
raised under the action of suprarenal extract, there is apparently no possibility 
of inhibiting the arterial contraction ; even the strongest stimulation of the 
depressor nerve, which under ordinary circumstances produces through the 
vasomotor centre a marked dilatation of the arterioles, is without result during 
the activity of this extract. The question naturally arises, How is it that the 
effect so soon disappears 1 In what manner is the active principle eliminated ? 
It is not eliminated by the kidneys, for the effect passes off just as quickly 
even although the renal arteries are clamped. It is not eliminated by the 
suprarenals themselves, for the same fact holds good for the suprarenals. It 
passes off almost equally quickly if the aorta and vena cava are tied in the 
upper part of the abdomen, so that there is no circulation of blood whatever in 
the abdominal organs. It is not oxidised or otherwise destroyed by the blood, 
for it retains its full potency even after it has been twenty-four hours in 
contact with that fluid. The most probable explanation of the disappearance 
of the effect seems to be that the active principle becomes packed away, and 
eventually rendered innocuous in certain organs. That the muscles take most 
part in this storage is probable, from the fact that the physiological effects upon 
the skeletal muscles are manifested for a long time after the effects upon the 
heart and arteries have disappeared. 
1 In man the effect of taking suprarenal extract by the month is to produce a general 
diminution in calibre of the arteries as measured by the arteriometer (Oliver, "Croonian 
Lectures," Lancet, London, 1896). 
2 li Proc. Physiol. Soc," Journ. Physiol., Cambridge and London, March 1897. 
