14 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [ III, I
(Plate IV, Fig. 1). The whorls of connective tissue thus formed become
hyalinised with very little cellular, nuclear contents then discernible (Plate III,
Fig. 1). There seems to be little doubt that the ova are usually transported by the
portal vessels into the organ, but very early lesions have been traced to the hepatic
vein, and no satisfactory explanation is forthcoming to throw light on the simul-
taneous involvement of the portal vein and the hepatic artery as seen in some
sections. The veins are more or less dilated. More marked changes are seen
around the larger veins but the smaller portal canals are not exempt. Brown
haematin-like pigment may be present in the endothelial cells of the organ or it
may lie free in the endothelial spaces. Apart from the nodular lesions, the portal
spaces reveal a considerable increase of newly formed, tortuous bile ducts and
connective tissue. It is interesting to note that in a very chronic case of the
disease, actual columns of liver cells in different stages of regeneration with the
provision of a fine system of capillary circulation in between the rows of hepatic
cells have been seen in the centre of a nodular lesion, the outer rings of the fibrous
capsule being completely absorbed (Plate VI, Figs. 3 and 4). This is presum-
ably an instance of a regenerating nodule attempting to set up liver function after
the toxic products and irritant ovum have been completely removed. In parenthesis,
it may be said that retrogressive changes in the capsule itself have also been
described by Theiler [1918], who states "Finally the capsule had completely
disappeared whilst the necrotic centre had increased and the nodule was surrounded
by a thin fibrillar envelope ". It has already been stated that the initial lesions
are practically restricted to the portal tract, the lobules themselves being singularly
free from any abnormality. However, lobular changes may be seen at a very
advanced stage of the disease. In this, a single ovum generally is seen lying at
some distance from the larger veins or an occasional egg may lie near a small vein.
Careful examination of these lobular lesions fails to reveal any evidence of the
muscular remnants of a broken down vessel. From this, it seems reasonable to
suppose that the lobular nodules usually originate in the finer capillaries and that
the delicate walls of these are not recognisable because of the changes which are
brought on by the pathological process. Nevertheless, it is not unlikely that now
and again an ovum does pierce through the vessel wall by means of its sharp spine
and finds itself in a perivascular situation. It may be mentioned here that no ovum
has been detected as actually piercing its way through the wall of a blood vessel
in spite of a careful examination of a very large number of stained sections. The
inter-lobular lesions may extend both in size and number and thus come to occupy
the position of the lobules, so much so that when the disease process is severe, whole
lobules may be altogether obliterated due to atrophy of liver cells and their replacement
by inflammatory tissue and proliferated bile ducts. But it is remarkable that the liver