A summary has been included at the end of each
section, but the scope of the thesis may be reviewed
by way of conclusion. Attention has chiefly been
directed to a study of anatomical and physiological
abnormalities in the peripheral arterial circulation.
Methods of investigation were described in the
first two sections. The pathological anatomy was
studied by gross dissection of amputated limbs
supplemented by histological and injection
technique. Physiological disturbances were
observed by performing exercise tolerance tests and
by measuring circulation .times by the reactive
hyperaemia and fluorescein methods. Particular
attention was paid to the use of the Greenfield
and Scarborough type of hand calorimeter and of
plethysmographs for the upper and lower limbs. The
majority of the observations have been made with
these two instruments and the precautions necessary
to obtain accurate readings were accordingly
detailed. An electrical capacitance manometer
designed for the direct recording of pressure in the
peripheral arteries was described.
The pathological anatomy of peripheral
vascular disease in the lower limbs was investigated
and the changes found in younger subjects with
thromboangiitis obliterans and in older subjects
with atherosclerosis were described.
Thromboangiitis involved chiefly the small distal
arteries of the extremity while atherosclerosis affected the larger more proximal arteries. In each disease the development of thromboses
obstructing the arteries and spreading to occlude
the origins of collateral vessels was responsible
for the onset of ischaemic gangrene. The recamalisation of obstructed arteries was studied in
detiaii, particulary with regard to the
development and function on of the elastic-coated
vessels seen penetrating the organised thrombus. The changes in blood flow and blood pressure resulting from these anatomical abnormalities were described. In diabetes mellitus of long standing
it was shown not only that there was a premature atherosclerosis of the arteries in the limbs, but
also that the smaller vessel were affected. Damage
to the latter might, in many cases, be chiefly
responsible for the development of symptoms of
ischsaemia.
The blood flow distal to a coarctation of the
aorta was investigated and it was shown that the
presence of this congenital abnormality did not
reduce the maximal circulatory capacity of the limbs
applied by the collateral arteries.
Popliteal aneurysms of atherosclerotic origin
were not associated with an unobstructed distal
arterial pathway. Clotting within the aneurysm was
a dangerous complication and the effect of such an
aneurysm was to reduced the distal circulation. On the other hand, a pulsating syphilitic aneurysm on
the axillary artery with the distal arteries unobstructed augmented the peripheral blood flow.
This increase beyond the reç±uirements of the distal
tissues led to the development of unilateral
clubbing of the fingers.
The blood flow distal to a coarctation of the
aorta was investigated and it was shown that the
prescence of this congenital abnormality did not
reduce the maximal circulatory capacity of the limbs
applied by the collateral arteries.
The circulatory changes associated with
clubbing were investigated in selected cases and it
was shown that an increased peripheral circulation
above the volume normally required by the tissues
was essential for the development of clubbing. The
excess blood was shunted through arteriovenous
anastomoses situated in the finger and to a lesser
degree in the toes and lobes of the ears. The
central mechanisms that might give rise to this
excessive peripheral blood flow were considered.
Tn general they led either to an output of blood
from the left ventricle greater in volume than the
requirements of the tissues supplied by the
systemic arterial circulation, or to an increase in
blood volume. The grossest degrees of clubbing were
seen when both factors together were operative.
The circulatory, changes brought about by the
infusion of noradrenaline into healthy subjects
were described. Three cases of phaeochromocytoma
were investigated particularly with regard to the
associated abnormalities in the peripheral
circulation. It was shown that persistent arterial
hypertension was not due to the continuous release
of noradrenaline into the circulation.
The investigations have thus been mainly
concerned with the study of arterial disease and
211
hypertension, the two major problems confronting
medicine today. They have been directed largely
towards the mechanism of the development of these
diseases and thus throw little light on their
underlying aetiology. No apology is, however,
reouired for this fact for elucidation of the
mechanism is the first logical step towards the
investigation of the fundamental underlying cause.
