_In horse._ With melanoma and atrophy, or without, pigment granules
fill hepatic cells, liver becomes brown or black. In calves. In sheep.
Apart from melanosis, the real cause unknown.
The accumulation of granules of black pigment in the hepatic cells has
been noticed in old and worn out horses (Louis Blanc, Cadeac,
Bruckmüller), in calves (Degive, Cadeac), and in sheep (Siedamgrotzky,
Barrier). In _horses_ it has been found in connection with atrophy, or
in other cases, with melanotic tumors in other parts. In atrophic cases
the liver is small, puckered, brown and dull, with a leathery appearance
on section, and with the hepatic cells charged with pigment granules so
that each acinus has a stellate appearance from the radiating lines of
cells. This constitutes _brown atrophy_.
The second form which may be called _melanotic liver_, is not associated
with atrophy, but is characterized by the crowding of the hepatic cells
with black pigment granules, which fill up the protoplasm and crowd the
still pale nucleus to one side. The affected portions become of a deep
black.
In _calves_ the pigmentation may be confined to the superficial portion
of the liver (Degive).
In _sheep_ pigmentation may be in the peripheral cells only of the
acinus (Cadeac) but is about equally distributed on the surface, and
throughout the interior of the liver, and may extend to the stroma of
the gland (Siedamgrotzky).
Apart from the general causes of melanosis, benignant or malignant, no
definite reason for this pigmentation has been assigned. The development
of melanæmia and tissue pigmentation in man from malarious
microörganisms suggests that other germs and their products may have a
similar effect in the lower animals but nothing certain is known as to
the true cause.
Apart from melanosis, it is not known that this pigmentation of the
hepatic cells is of any essential pathological importance. It is
important however for the veterinarian to be acquainted with the
condition, that he may intelligently deal with such lesions whether seen
in ordinary post mortem examinations, or in the course of meat
inspection.