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BULLETIN OF THE BUREAU OF FISHERIES. 
In the United States the disease has been known to fish culture for some 40 years, 
but has escaped mention, so far as we have been able to find, in the several treatises on 
fish culture which have been written in this country, and has not until recently been the 
subject of any particular study. 
From time to time during the progress of this investigation we have made prelimi- 
nary statements before the American Association for Cancer Research. These brief 
summaries are here reprinted in order to show the development of the investigation along 
the lines originally indicated. 
AN EPIDEMIC OE CARCINOMA OF THE THYROID GLAND AMONG FISH.“ 
Dr. Harvey R. Gaylord, Buffalo: This paper is a continuation of a preliminary report made before 
the society a year ago. It gives details of two epidemics in different parts of the coimtry, and refers to 
two others. The epidemic referred to last year, which resulted in the loss of 3,500 brook trout, had, 
during the summer of 1909, begun to involve the brown trout and adult rainbows, so that heavy losses 
continued during this summer. Among the fish preserved from this epidemic was one with a tumor 
on the lower jaw, which on section was found to be either an implantation of the thyroid tumor or a 
metastasis, as the fish so affected had a primary tumor of the thyroid. From this observation it is plain 
that this tumor may, under given conditions, metastasize, or that it is implantable. In an epidemic 
in a second hatchery, an analysis of the course of the disease again showed that where fish occupied 
ponds which received water from ponds containing infected fish, these fish may become infected; 
and, furthermore, the rate at which the fish become involved increases progressively as the contents 
of ponds containing infected fish are added to the water which supply the fish. Another observation 
of importance is the discovery that lots of fish are immune. This is particularly shown in hybrid fish, 
in which one lot of hybrid salmon i year old were reduced from 1,043 April to 44 sound fish remain- 
ing in August, whereas another lot of yearling hybrid salmon, although badly exposed by being placed 
in ponds into which the water from infected ponds ran, remained free from the disease throughout. 
Three lots of Scotch sea trout remained immune, althongh badly exposed. The only lot of brook trout 
2 years old which were free from the disease was found on a careful analysis of their position throughout 
their entire life history in this hatchery, never to have been placed where the water from infected troughs 
or ponds flowed to them. They were placed in the uppermost pond and remained free from the disease 
throughout the epidemic. These observations on immunity in hybrid fish, in the light of those made by 
Tyzzer in inoculation of Japanese waltzing-mouse tumor, in hybrids from immune and nonimmune 
parents, serve to accentuate the similarity of tliis disease in fish to cancer in warm-blooded animals. 
The disease is found to affect very small fish. A brook trout of the hatch of 1909, 3 inches in length, 
was shown with a tumor of considerable size from which it had died. This was the first affected fish 
from the hatch of 1909, and it had occupied from May until September one of five troughs which had 
the previous summer contained infected fish. From this it would appear that the contagion can be 
localized, even to given, small wooden troughs, and that these troughs can retain their infectivity from 
year to year. In all the epidemics thus far described, occasionally large fish, when exposed, acquire 
the disease. A landlocked salmon 8 years old, measuring 24 inches in length, developed large tumors, 
and in two other hatcheries during the past year epidemics have broken out involving considerable 
numbers of adult rainbow trout and large adult brook trout. Among the large fish epithelioma of the tongue 
or the region of the mouth is not uncommon. Carcinoma of the thyroid produces the most rapid destruc- 
tion among young fish, frequently diffusely infiltrating the gills and also growing to great relative size 
in the small fish. The tumor erodes bone, destroys cartilage, and infiltrates the muscular structure. 
The tumor presents varying characteristics, frequently retaining the alveolar type with colloid, again 
of a strictly adenomatous type, but in all cases with areas of complete malignant degeneration and 
assuming the characteristics of solid soft carcinoma. 
o American Association for Cancer Research, meeting of Nov. 27, 1909, Journal American Medical Association, Jan, 15, 1910. 
