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 groimd in this affection. The 

 evidence of infectivity and contagion appear to the obser\'er 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 \ FISH II.^TCHERY." 



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 bro^-n 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 the 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 kno\^•n 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 witli 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 tmdertaking 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 vfith 

 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 Salmonidae, 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 191 1 Marine 

 and Lenhart published photomicrographs of normal thyroid in the brook trout in 

 illustration of studies of enlargement of the gland. Thompson in 191 1 published a 

 paper on the thyroid and parathyroid of vertebrates, with Amiurus as the only teleost 



a American Association for Cancer Research, meeting of Nov. 27, '908, Journal of American Medical Association, Jan. 30, 1909. 



