CARCINOMA OF THE THYROID IN SALMONOID FISHES. 453 



EXPERIMENTAL PRODUCTION OF THE DISEASE. 



TROUT TUMOR MATERIAL IN STANDING WATER. 



The contents of a thyroid tumor of a trout were expressed into tap water and brook 

 trout fry in the sac stage were introduced. About 300 fry were used, distributed in 15 

 shallow open dishes each with from i to 2 liters of the contaminated water. Eighty- 

 five fry in similar dishes constituted the control. By keeping the dishes in the cold the 

 fry were maintained for 23 days without change of water, or other than spontaneous 

 surface aeration. During this period a loss of 16 per cent occurred on the fish in the 

 tumor water and 1 1.7 per cent on the controls. 



After removal from the tumor water the fry and their controls were held for sev- 

 eral weeks in flowing tap water and suffered a gradual mortality. Sectionsof the thyroid 

 region of these fish show no recognizable difference between the controls and those fed 

 the thyroid material. Figure 13 shows the thyroid of a control fish soon after the food 

 sac had been absorbed. 



FEEDING TROUT THYROID TUMOR. 



Fourteen brook trout of yearling age but of small size, reared almost entirely on 

 live fish food, were fed nine times during one month with portions of fresh thyroid trout 

 tumor. The fish were held for 54 days in glass jars, containing each 3 liters of water 

 and two individuals. The water was changed once during this period. The tempera- 

 ture ranged from a little above the freezing point to 17° C, which made necessary their 

 removal to flowing water. They had received no other food than tumor material. 

 When transferred there was no external evidence of thyroid enlargement. No histo- 

 logical changes in the thyroid tissue were recognized after careful comparisons with the 



controls. 



FEEDING HUMAN CANCER LIVER. 



Under the same general conditions as in the preceding experiment 12 trout were 

 fed five times during 23 days with solid human cancer material from metastatic foci in 

 liver of gastric carcinoma. After 54 days they were transferred to flowing water. All 

 were without externally visible thyroid change and showed microscopically the same 

 early hyperplastic stage as the controls. 



CLOSED QRCULATION. 



In order to experiment further with normal and tumored trout in unchanged water, 

 two independent aquarium systems were established for using the same water over 

 again continuously by means of circulation, aeration, and filtration. Refrigeration was 

 also provided so that the water could be at all times kept at a suitable temperature for 

 trout. 



During 51 days, 16 domesticated brook trout were fed human cancer of the liver on 

 14 different days, and became reduced to 8 fish in number. The thyroids of 4 of these 

 were affected and 2 had visible tumors, but an accident prevented the controls from 

 covering an equal period, and though the latter, 12 in number, were all clean but one, 

 nothing conclusive is to be inferred. 



