548 TRANSACTIONS OF SECTION I. 
dilators. Thirdly, with certain exceptions, cardiac and arterial innervations 
appear co-ordinated—the vagi with the dilator, and the accelerators with the 
vaso-constrictor mechanisms. 
Hyidence of venous innervation :— 
(1) Venous pressure in asphyxia-rises either simultaneously with, or subse- 
quent to, the rise, and after the fall to zero of arterial blood-pressure. 
(2) Venous pressure rises either simultaneously with, independently of, or 
it fails to rise with, the rise of arterial blood-pressure upon the intravenous 
injection of adrenalin, epinine, or pituitary. Moreover, it may rise and fall 
and rise again during the period of raised arterial pressure upon intravenous 
injection mentioned. 
(3) During syncopal fall of arterial blood-pressure the bowel volume markedly 
diminishes. This occurs whether the animal be prore or supine, and whether 
the heart’s rate be greatly or slightly retarded. Such fall in arterial blood- 
pressure is accompanied by a rise in venous blood-pressure and arterial vaso- 
dilation, as is well shown in the syncope induced by clamping the brain 
arteries, in which case the heart’s rate is practically constant. The only inter- 
pretation which seems possible is that of venous constriction. 
The possibility of interpreting these results as due to varying intra- 
abdominal tension from muscular action, or to alterations in cardiac output, or 
to blood displacements or changes in arterial tension, was found to be inade- 
quate to explain the phenomena. Venous innervation seems to be the only 
interpretation possible. 
The frequent association of vagus inhibition of the heart—as represented 
by a retardation of rate ranging from moderate slowing to actual heart-stop— 
with a rise of venous pressure, cannot be ascribed to dislocation of blood as 
a result of diminution in the heart’s output, because it occurs whether the 
arterial blood-pressure be falling or rising. Similarly the fall of venous 
pressure constantly associated with accelerator action cannot be ascribed to 
dislocation of blood by arterio-constrictor retention, since it occurs whether 
the arterial blood-pressure be low or rising. Moreover, the venous blood- 
pressure may be found both high and low in a single tracing, in which, through- 
out, the arterial blood-pressure is high, but in which vagal action is temporarily 
replaced by accelerator, during which temporary period the venous pressure 
falls and remains low till vagal action is restored. It points to co-ordinate 
innervation, and further to reciprocal relations between the vagi and venous 
dilators on the one hand, and the accelerators and venous constrictors on the 
other. 
Examination of a larger number of blood-pressure tracings shows a constancy 
of co-ordinate innervation of the cardiac accelerator with vaso-constrictor, and 
again of the cardiac vagus with vaso-dilator mechanisms. They furthermore 
indicate a reciprocal relation between these groups. There are accountable 
exceptions in asphyxia, adrenalin and other intoxications, depressor nerve 
excitation, a depression of the vagi, &c. Syncopal fall of arterial blood-pressure 
with cardiac slowing is constantly associated with vaso-dilation, whilst sudden 
rises in arterial blood-pressure show more or less the incidence of accelerator 
rhythm, which may or may not be due to increased secretion of the suprarenals. 
6. Artificial Collateralisation as applied to the Abdominal Aorta. 
By Bast, Kinvineton, M.S. 
Cases have been found post-mortem where the abdominal aorta has been 
completely occluded, yet life has been possible, This has been caused by certain 
pathological conditions which act gradually. 
An attempt was made to imitate this gradual occlusion by ligaturing the 
abdominal aorta in two stages. The first operation consisted in partly obstruct- 
ing the aorta by a silk ligature applied a short distance above the bifurcation 
into the two iliac vessels. It was impossible to gauge accurately the narrow- 
ing, but, as a rough test, the ligature on the aorta was tightened till the 
pulsation was just, though definitely, perceptible to the finger applied where 
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