CARCINOMA OR THE THYROID IN 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, ii lots each of 50 adult wild trout from Wisconsin were placed 
in 1 1 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 effect 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 2151 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 viii). 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 few showed a considerable 
“ We believe that these experiments, reported at the fifth annual meeting of the American Association for Cancer Research, 
April 3 and 4, r9i2, in Philadelphia, and reported in the Zeitschrift fiir Erebsforschung, Band 12, Heft 2, 1912, p. 436, under the 
title, “ Relation of Feeding to Thyroid Hyperplasia in the Salmonidae,” by H. R. Gaylord and M. C. Marsh, Buffalo, constitute 
the first instance in which spontaneous cancer has been experimentally induced imder properly controlled conditions in the 
lower animals. They antedate the recent experiments of Fibiger in the prodnction of carcinoma of the stomach and esophagus 
in rats by feeding them nematodes from cockroaches, for which a similar claim has been made. 
