CARCINOMA OF THE THYROID IN SALMONOID FISHES. 
373 
In the study of this interesting form of cancer, the discovery of metastasis formation, the evidences 
of immunity, and the influence of blood relationship to susceptibility show the practical identity of 
this affection to cancer in warm-blooded animals. The apparent absence of metastasis formation as a 
criticism was long since applied to mouse cancers and to-day falls to the ground in this affection. The 
evidence of infectivity and contagion appear to the observer to be conclusive, and when correlated in 
the evidence of infectivity in cancer in warm-blooded animals should prove the greatest support to the 
parasitic theory we have yet encountered. The marked evidence of infectivity and contagion found 
in carcinoma of the thyroid in fish appears to be an accentuation of similar evidence of a less convincing 
character found in other species. Its accentuation in this disease can be largely explained by the envi- 
ronment and the conditions under which fish are artificially propagated. 
AN EPIDEMIC OF CANCER OP THE THYROID IN BROOK TROUT IN A FISH HATCHERY. “ 
Dr. H. R. Gaylord, Buffalo: This is a preliminary report on the investigation of a fish hatchery in 
which an epidemic of carcinoma of the thyroid in 2-year-old brook and brown trout exists at the 
present time. In this hatchery the water supply is from a spring coming out of a hillside, which runs 
into a basin or pond, from which it is piped to a small reservoir and then through a series of tanks which 
draw their supply directly from the reservoir. Carcinoma of tlie thyroid was discovered in a fish in the 
basin on the hillside two years ago. One year ago this basin was emptied and restocked with young 
fish and feeding was practiced for the first time in this upper pond. Of the tanks fed from the water 
passing through this pond, one tank containing 3,700 brook trout 2 years old, hatched from eggs brought 
from a hatchery in an adjoining State where the disease is not known to exist, showed 700 fish in various 
stages of the disease. The outbreak occurred in the early autumn and fresh cases are continually devel- 
oping. In an adjoining tank, which has no connection whatsoever with the tank in question, are 200 
brown trout reared from eggs hatched on the premises. Between 3 and 4 per cent of these fish show 
disease. The infected fish at no time have come in direct contact with the fish in the upper pond 
where the disease is known to have existed ; neither at any time have the brook trout and the brown trout 
been in contact with each other. I believe that the state of affairs found in this fish hatchery points 
very strongly to the infectious nature of this form of cancer and that the contagion is water-borne. It 
is possible that feeding liver into the waters of the fish hatchery has some relation to the outbreak in this 
case. I know of a second fish hatchery where the disease was endemic for a number of years and where 
the feeding of liver has been changed to the feeding of chopped sea fish and in the last three years the 
disease has disappeared. I also know of two other fish hatcheries in which the disease is endemic, and 
I am undertaking a systematic and careful study of a number of fish hatcheries for the purpose of further 
determining the conditions under which the disease occurs. 
NORMAL THYROID IN SALMONOIDS. 
The thyroid in fishes has given rise to a not inconsiderable literature, beginning with 
Simon’s paper (1844) on the comparative anatomy of the gland, in which he first identified 
the thyroid in fishes. The detailed studies of its histology belong to a much later period. 
Most of the work has been upon genera outside the Salmonidte, and especially upon the 
lower forms of fishes. Maurer (1886) described and illustrated the development of the 
thyroid in a trout, and the location of the thyroid follicles in the adult, with a semi- 
diagrammatic drawing of the histology of the adult follicles. In 1910 and 1911 Marine 
and Lenhart published photomicrographs of normal thyroid in the brook trout in 
illustration of studies of enlargement of the gland. Thompson in 1911 published a 
paper on the thyroid and parathyroid of vertebrates, with Amiurus as the only teleost 
o American Association for Cancer Research, meeting of Nov. 27, 1908, Journal of American Medical Association, Jan. 30, 1909. 
