ETIOLOGY OF ENZOOTIC BOVINE HAEMATURIA                    351

from the provinces the same obscure structures were detected, and the possibility
of a Schistosome origin was suggested. In the Annual Report for 1932-1933 (p. 15)
the failure to obtain confirmation of the above suggestion has been mentioned, but
the observation of ' a definite host reaction ' against the ' bodies ' left no doubt
that they were parasitic and foreign (Plate XXIX, Fig. 1). In size they were larger
than the usual body cells, and they definitely had a greater depth of focus. Since
an occasional' body ' appeared to have engulfed rare red corpuscles, or to possess
a vacuole they were described in the above Report as ' peculiar macrophage-like
cells,' and the possibility that these were Entamoeba was pursued by means of the
cultural technique of Boeck and Drbohlav [1925]. The first results have already
been mentioned in the Annual Report of 1932-33. Before giving a preliminary
description of the causative parasite, which appears to be responsible for this
disease, it is essential that the minute histology of the condition be first described
in the light of fresh knowledge, since the current views are faulty in some respects.

                           PATHOLOGICAL HISTROLOGY.

The Urinary Bladder. One would not expect to detect a case of
bovine haematuria at its very commencement with a view to studying
the pathological process in its earliest stage. Young and old lesions are, however,
present in most cases and these may be utilized for histopathological
studies. The disease is primarily an affection of the submucous layer, inflam-
atory exudation into which leads to necrosis and consequent ulceration
of the mucous membrane. The bladder is intensely congested, and the blood vessels
supplying the mucous and submucous layers are greatly dilated (Plate XX, Fig. 2).
The capillary vessels are often ruptured, and extravasation of blood around them is
to be seen. In some cases however the whole of the bladder wall is extensively in-
filtrated with blood and its pigments. The vascular endothelium is damaged to a
certain extent, and the exudation of serum to the perivascular regions leads to a
pushing apart of the surrounding connective tissue. Sometimes oedema is very
pronounced, and is easily discernible immediately below the muscularis mucosa and
in the strands of tissue, which intervene between muscle fibres.

The diversity of the pathological processes and the extent of their severity seen
in each case, depend upon the degree of the parasitic infestation, rate of division of
the parasites, and upon whether the lethal effects are repeated over a length of time.
The susceptibility of the affected bovine or its bodily resistance must also be a
factor of importance in the pathogenesis.

As a result of the inflammatory exudation, the epithelial lining of the bladder
is swollen and elevated, the inflammatory products separating the mucosa
from the thickened submucous layer. The extravasated blood and exuda-