J. F. SHIRLAW 175
tissue somewhat granulomatous on superficial aspect. Histological examina-
tion of this tissue shows it to be relatively normal tissue resulting from the
proliferation of the fixed connective tissue elements of the part, with a mild
degree of mononuclear infiltration, and a certain proportion of eosinophiles.
There is no tendency to focal necrosis or aggregation of leucocytes with vascu-
lar congestion and secondary inflammatory changes such as characterise an
infective process. The appearance of the new tissue is indicative, on the other
hand, of a connective tissue cell hyperplasia dependent on functional
derangement of the vascular supply of the tissues, leading to the oedema
which characterises the earlier lesions. The oedematous fluid distends the
subcutaneous tissue along the channels of least resistance, being limited only
by fascial planes which maintain the fluid under pressure. Examination of
the fluid proves it to be purely transudative. The blood vessels of the new
tissue show various stages of a process culminating in total occlusion. There
is no thrombosis but rather an insidious and progressive mesarteritis resulting
in a gross thickening of the vessel wall and a constriction and fin al obliteration
of the lumen. The tunica intima and the endothelium appear passively to
resist the encroachment of the new formative tissue derived from the tunica
media until it appears that the narrowing of the vessel evokes an eventual
response on part of the intima with a final endarteritis obliterans. The vasa
vasorum of the adventitium show a marked proliferation, and an incipient
thickening of the parent stems.
Synchronous with this process leading to destruction of the structure
and function of the arteries there is noted an attempt at the formation of
new arteries (establishment of collateral supply?) but even these, before they
have attained any dimension, commence to participate in the pathological
changes affecting the parent vessels. The veins are seen to be dilated to maxi-
mum capacity and the explanation of the tissue oedema in an early case
appears obvious. The lymph vessels are equally distended, show considera-
able attempt at proliferation, and appear blocked with coagulated lymph
which has retracted from the walls of the vessels. In three cases, there was
an extensive thickening and occlusion of all the vessels of the affected
limbs. These vessels, both arteries and veins, appeared as thickened cords
and it was impossible to determine an existing collateral circulation. In
one of these cases, necrosis was so absolute as to lead to sloughing of the worst
affected limb just above the femoro-tibial articulation. Similar lesions
affecting the vascular supply are seen in the tail and ears.
It will be seen, therefore, that the superficial lesions depend upon a gross
derangement of the vascular system of the extremities of the body. On
histological examination of the tissues, no apparent etiological factor can be
determined. It is evident that the process is insidious and unaccompanied
by any inflammatory change, an observation which is validated by the failure
to isolate any organisms of pathogenic significance from the substance of the
lesions.
The examination of teased specimens of tissue and the serial