BLACK TUMOR OF THE CATFISH' 
By RAYMOND C. OSBURN 
Professor of Zoology, Ohio State University 
A conspicuous and very unsightly disease of the common bullhead, or horn- 
pout (Ameiurus nehulosus LeSueur) , appeared a few years ago in a pond at Wau- 
quoit, near Falmouth, Mass. The tumorous excrescences produced by the disease 
are so striking that it seems almost impossible that no mention of it has been made 
in the scientific literature. Ichthyologists and fish-culturists consulted have pro- 
fessed their ignorance of the existence of the disease, and examination of the litera- 
ture of fish pathology proved futile. 
The keen-eyed Thoreau, however, did observe the bidlheads of the Concord 
River to be affected with this trouble more than 70 years ago. I should have over- 
looked this reference to it but for the kindness of Henry W. Henshaw of the United 
States Biological Survey, who called my attention to certain statements in Thoreau's 
"Journal." Under date of July 10, 1852, that writer states: "One of these large 
pouts had a large velvet-black spot, which included the right pectoral fin; a kind 
of disease which I have often observed on them." The location was on the Concord 
River. Later (July, 1858) Thoreau again wrote in his "Journal": "I see a pout 
this afternoon in the Assobet" (a tributary of the Concord) "lying on the bottom 
near the shore, evidently diseased. * * *_ Nearly half the head, from the snout 
backward diagonally, is covered with an inky-black kind of leprosy, like a crusta- 
ceous lichen." There can be no doubt that Thoreau observed the disease which 
forms the subject of the present paper, but it seems strange that so long a period 
should elapse before such a striking malady should again come to the attention of 
a naturalist. 
In the summer of 1917, while I was spending a short time at the Marine Bio- 
logical Laboratory at Woods Hole, Mass., the late Vinal Edwards, collector for the 
Bureau of Fisheries, brought me a specimen of the diseased fish and asked my 
opinion of the nature of the growth. I took the opportunity to visit the pond where 
the disease occurred and collected some more material for preservation for sec- 
tioning and made some photographs. The best I could do at the time was to pro- 
nounce the disease some form of a tumor, and this opinion was concurred in, with- 
out any further information, by several pathologists to whom material was sub- 
mitted. 
In the summer of 1919 the Bureau of Fisheries made possible my further study 
of this disease, and I spent six weeks at the Woods Hole station. My results, 
though not complete in every detail, have been satisfactory. 
1 A very brief account of this disease has already been published in Bureau of Fisheries Doc. 896, Progress in Biological 
Inquiries, 1920, p. 17. 
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