CARCINOMA OF THE THYROID IM SALMONOID FISHES. 457 



months, when one thyroid tumor and two red floors had developed among them. The 

 controls had been previously lost from some unknown cause, leaving the result negative. 



EXPERIMENTAL INDUCTION OF CARCINOMA." 



In June, 1910, about 2,400 wild brook trout of various sizes were collected in the 

 wilderness of Wisconsin by the Bureau of Fisheries and brought to Craig Brook station. 

 They were held in Craig Brook above all fish cultural operations until used in experi- 

 ments. Several specimens were sectioned from time to time and found to be entirely 

 normal. A series of 16 new cement tanks, 2.7 by i by i meters in size, which had not 

 previously held fish, were used as containers for the experimental lots. (Fig. 79 left.) 

 The depth of water in these tanks was 0.8 meter and the inflow 50 to 60 liters per 

 minute. In July, 1910, 11 lots each of 50 adult wild trout from Wisconsin were placed 

 in II of these tanks and feeding experiments begun with a variety of foods, which were 

 maintained for each lot throughout the experiment without change. The so-called 

 natural food was not all of one kind, but consisted of fresh-water mussels, fresh-water 

 fish, and in the summer maggots of flies. The vegetable food was screenings from 

 miscellaneous grains. In September, 1910, certain of the lots were augmented by smaller 

 wild trout from Wisconsin, which had received food corresponding to the lots to which 

 they were added, or natural food. 



Table viii summarizes these feeding experiments and includes some smaller lots 

 which were inoculated in various ways, and were fed natural food. Such lots were 

 negative, and are in eff'ect controls to the feeding experiments. The inoculated lots 

 are discussed under a separate heading. Lot 2149 was an attempt to crowd the fish 

 by confining them in one-third of the tank. Lot 2155 aimed at excess feeding. 



Lots 2150 and 21 51 were practically wiped out by the unsuitable food, to which the 

 wild trout could not adapt themselves readily. The wild trout gradually became 

 accustomed to the fish cultural foods, liver and heart, and finally thrived upon them 

 about as domesticated trout do. On examination after four months, and again after 

 one year, all the fish were clinically clean, without any external evidence of thyroid 

 disease. At the examination after one year the thyroid region of from one to three 

 fish from each tank was prepared for microscopic study, and the histology of each is 

 shown below by a description of each section by number (table vni). The diagnoses may 

 be briefly summarized as follows: 



In the lots fed raw liver (fig. 84) and heart (fig. 85) a general hyperplasia existed 

 with early carcinoma in a few cases; the two fish from lot 2155 were exceptional, appear- 

 ing normal. The lot fed cooked liver had remained normal. (Fig. 87.) Those fed 

 marine fish (fig. 88), vegetable food (fig. 89), and natural food (fig. 86) were entirely 

 without hyperplasia. Nearly all remained normal, but a fev/ showed a considerable 



a We believe that these experiments, reported at the fifth annual meeting of the American Association for Cancer Research, 

 April 3 and 4. 1912, in Philadelphia, and reported in the Zeitschrift fiir Krebsforschmig. Band 12. Heft 2, 1912, p. 436, under the 

 title, " Relation of Feeding to ThjToid Hyperplasia in the Salmmiida," by H. R. Gaylord and M. C. Marsh, Buffalo, constitute 

 the first instance in which spontaneous cancer has been experimentally induced under properly controlled conditions in the 

 lower animals. They antedate the recent experiments of Fibiger in the production of carcinoma of the stomach and esophagus 

 in rats by feediag them nematodes from cockroaches, for which a similar claim has been made. 



8207^—14 7 



