CARCINOMA OF THF THYROID IN SARMONOID FISHES. 
455 
tember i, 1909, and killed for examination November 24, 1909, showed at the point of 
inoculation, which was in the muscular structure of the abdominal wall, just anterior to 
the left ventral fin, evidence of a small protruding growth the size of a grain of rice. On 
sectioning this tissue, a slender growth is found extending in what must have oeen the 
track of the needle. Under the microscope the growth is made up of a series of nodules, 
most of them with a not very well-defined connective tissue capsule. The continuity 
of the epidermis at the point of the small tumor is broken, and we have here a growth of 
tissue connected with the nodular growths in the deeper structures. This protrudes 
through the broken continuity of the epidermis. The circumscribed nodules lying be- 
tween the muscle bundles and the subcutaneous tissue are made up of large spindle 
and irregularly shaped cells. The centers of the larger nodules contain a certain amount 
of hyaline detritus. Scattered between the cells of the nodules, particularly toward the 
center, are many leucocytes. At the outer margins of the nodules the cells are best 
preserved. The nuclei vary greatly in size, the protoplasm stains, the cell boundaries 
are not always well defined. The growth is made up of a complex of cells with large 
vesicular nuclei containing one or more nucleoli. They may be recognized as thyroid epi- 
thelium. In a nodule which fills the break in continuity in the epidermis there is a dis- 
tinct suggestion of tubular arrangement with a definite stroma carrying blood vessels, 
and at the margin of one or two of the other nodules definite alveoli may be made out. 
Toward the centers of the nodules there is distinct evidence of atrophy of the cells, 
associated with clumps of chromatin and hyaline detritus. There are many cells with 
very large nuclei. There is generally a great difference in the size and shape of the 
nuclei. Rarely a karyokinetic figure is found. The cells are closely packed together, 
but in some nodules there has evidently been a growth of capillaries in attempts at forma- 
tion of a stroma. From the microscopic picture it is evident that there has been some 
proliferation in the implanted tissue, and that three months after portions of the graft 
at least are still alive. 
At Craig Brook station in 1910 implants were made directly into the thyroid region 
of the fish with the aid of a hypodermic needle. It was found that the trout will endure 
a needle puneture in the floor of the mouth and the injection of one-fifth cubic centimeter 
of physiological salt solution directly into the tissues containing the thyroid with little 
reaction. By inserting the needle a little to one side of the median line the ventral 
aorta is avoided, and most of them show no external bleeding. Some of the fish suffer 
from shock, due to the puncture, from which they recover within 5 to 20 seconds. Even 
those which bleed usually do not succumb. Of 76 yearling domesticated trout thus 
inoculated as controls, only i died as a result of the manipulation. The fish tumor 
material for inoculation was ground up and mixed with its own volume of physiological 
salt solution. The difficulty in planting this material in the tissues of the trout lies in 
the high toxicity of the tumor extract. It is not practicable to place transplants of 
ordinary size in this vascular region without heavy loss from toxemia. The tumor 
material varies considerably in toxicity. Domesticated trout endure the mechanical 
injury incidental to inoculation better than wild trout. 
