122 
ON MELANOSIS. 
By Mr. J. D. Harrison, Southport. 
In October 1822, Messrs. Cullen and Carswell had an opportu- 
nity of seeing and examining a horse labouring under that very 
curious disease, termed Melanosis. The animal was emaciated, 
and seemed to have been long under the influence of the disorder. 
During life they saw a number of tumours — hard, but moveable — 
under the root of the tail, and in the neighbourhood of the rectum. 
Under the delicate mucous membrance of the verge of the anus 
they were seen of a deep black colour. On the left buttock an 
enormous mass of the same was felt immediately under the skin, 
but connected with the deeper parts. In the centre of this mass 
was an ulcerated opening, from which a foetid pus issued, mixed 
with small pieces of the melanosis. 
On dissection, great masses of this substance were found in other 
places besides the cellular texture. There were many seated at 
the root of the neck on the right side, partly in the cellular sub- 
stance lying between the muscles, and partly in the very substance 
of the muscles. There were a few near the apex of the scapula, un- 
der the panniculus carnosus. Some were found in the groin on the 
same side and in the seat of the superficial absorbent glands. They 
noticed one large mass of the shape and size of an orange between 
the 6th and 7th ribs of the right side, which had originated in the 
substance of the intercostal muscles, and had increased inwardly so 
as to raise the pleura from the subjacent bone and muscular strata. 
The peritoneum had melanotic matter lying upon that part where 
(leaving the bladder and rectum), it gives a covering to the last 
lumbar vertebrae. The pleura in several places was similarly af- 
fected, and chiefly where it forms the mediastinum and gives a co- 
vering to the pericardium. From near the termination of the aorta, 
down the lumbar region on the left side, into the pelvis by the side 
of the rectum, and out of it by the exterior aperture, there extended 
an immense chain, beginning above by one or two small insulated 
tumours situated on the aorta, gradually increasing in bulk, until at 
last the black matter formed masses near the anus, as large as a 
child’s head. From the anal region the disease appeared to have 
spread into the muscles of the buttock. 
Such were the situations in which this curious disease was found, 
the substance of all the viscera being quite healthy. 
After a careful examination, Messrs. Cullen and Carswell be- 
came satisfied that the large masses of melanosis were a congeries 
of smaller ones of different sizes. Each was surrounded by a cyst 
