ON MELANOSIS. 
123 
of condensed cellular membrane. These cysts did not communi- 
cate, but merely adhered together, thus forming large masses. Some 
of the individual cysts were no larger than peas, others as large as 
an apple, and of all intermediate magnitudes. The investing cysts 
of the melanosis situated in other structures than the cellular mem- 
brane (as in the muscular structure), were remarkably thin, so as 
in some places to be scarcely detected. The tumours, when cut into, 
were all of a deep black colour, similar to the pigmentum nigrum 
of the eye, or China ink. Most of them were as hard as cheese, 
while others were much softer. The vessels in their vicinity were 
not enlarged. Nerves were sometimes seen running over the sur- 
face, or sometimes traversing the very substance of the black masses, 
but without any cognizable change in the nerves themselves. The 
surrounding muscular texture was unchanged, and seemed merely 
separated in its fibres for the lodgment of the melanotic matter. On 
the pleura and peritoneum the disposition of the melanosis was 
somewhat different. It was effused on the surface of these mem- 
branes, not in round masses, but in streaks and patches. There 
seemed to have taken place on their surface a formation of cellular 
tissue, into which the black matter appeared to have been poured 
out, for it could be scraped off, and the serous coat was still left 
smooth and entire. The matter, too, was much softer, so as to be 
semifluid. The membranes upon which it was formed bore no traces 
of vascularity. 
The striking appearances as above recorded are often met with 
in horses, not in general to such an extent, but sufficiently so to 
stamp its character and entitle it to a place in veterinary nosology. 
The notice of the profession having been drawn to it by Mr. Jackson, 
I have been induced to transcribe the foregoing case as being more 
illustrative of its peculiarities than any thing I can say from my own 
persona] knowledge, though I have seen many cases, and can bear 
Mr. Jackson out in saying that it is most frequently observed in 
white horses : still I have seen it in horses of all colours and grades. 
I can likewise vouch for the accuracy of the following observations, 
drawn from the same source, viz. the Medico Chirurgical Review 
for Jan. 1825, and they embody ail that is at present known re- 
specting it. 
“It appears that melanosis may exist independent of any altera- 
tion of structure : it may also exist where there is alteration of 
structure, as in pneumonia, &c. forming a symptomatic disease, 
whereas in the first it is idiopathic. 
“There is a great distinction between the disease under consider- 
ation and cancer and fungus hsematodes. Scirrhus chiefly attacks 
glandular structures that have been previously in a state of inflam- 
mation; while haemato-fungoid tumour attacks every kind of tex- 
