ETIOLOGY OF ENZOOTIC BOVINE HAEMATURIA
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cosal vessels are the first to exhibit the lesions of the disease, and like inflammatory
conditions in other diseases, new vessels are produced in this situation. The majori-
ty of the vessels are more or less dilated, and this dilatation is accentuated in some
places more than in others. The endothelium of individual vessels shows
proliferation and desquamation, and the lumen contains some of the active forms of
the parasite. If thrombosis of a vessel occurs, and this is aided by the parasites
being in the sluggish stage, the arrest of the parasites takes place (Plate XXIX,
Fig. 1). A process of fibrous encapsulation from the periphery inwards takes place,
and an attempt at the digestion of individual parasites is made by the body cells
(Plate XXIV, Fig. 2). The affected vessels undergo varying degrees of endarteritis
obliterans. Some vessels are actually obliterated, and in others partially sclerosed,
a few parasites may still be seen to persist (Plate XXIX, Fig. 1). The localisa-
tion of parasites in altered vessels has been seen at all depths to the subserosa.
In the continuity of the bladder epithelium, one often notices several solid nests
of epithelium, which are generally disposed in the form of rounded adenomatous
cysts but apparently without any central lumen. Various stages of development
and degeneration of these epithelial nodes are seen (Plate XXIII, Fig. 1). As these
nodes enlarge, their central zone shows some thinning, while a few prominent
nucleated " bodies " are clearly seen. With further development of these nodes,
the nucleated " bodies " show more structural differentiation, and when the evidence
of rare parasitic encystment is observed one has no hesitation in recognising the
initially undifferentiated nucleated " bodies " as the forerunner of the larger sized
parasites or of their encysted fellows (Plate XXIII, Fig. 2). The collection of
several layered epithelium in nodes appears to be more frequent than the normally
existent mucus-secreting glands of the bladder, and evidence seems to be available to
show that a number of these nodes may originate from the bladder epithelium (Plate
XXII, Fig. 1). Since a number of such nodes are also seen to be present in the
depth of the bladder, there need be little doubt that they can originate from blood
vessels. Further it seems possible that the papilliform processes of the mucosa, as
they grow, may close and form tubular adenomatous structures. Degenerative
changes in the nodes extend from the centre towards the periphery, and in the ad-
vanced stages all the epithelial cells may be destroyed, giving place to a collection
of an increasing number of parasites. The enclosing membrane then bursts, and
the parasites are liberated into the urine (Plate XXV, Fig. 1).
In the most oldstanding cases, the blood vessels at all depths of the bladder
wall show an extreme proliferation of the endothelium and appear as only collec-
tions of epithelial cells, bearing little or no resemblance to the original blood vessels.
In some cases these epithelial cells exhibit a definite infiltrative type of extension,
and show unmistakable tendency to simulate malignancy (Plate XXVIII, Figs. 1