372 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 OF 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 country, 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 m 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, although 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 this 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. 



