CARCINOMA OR THE THYROID IN SARMONOID FISHES. 407 
We have expressed our reason for holding that the growths on the apex of the 
jaw and this growth in the wall of the intestinal tract just within the anus are instances 
of genuine metastasis formation. We believe that a wider understanding of the natural 
history of carcinoma of the thyroid of the Salmonidae will show that a case described 
by Marine and Lenhart (1911a, p. 470) is more probably a metastasis than a tumor 
springing from misplaced thyroid. These authors describe an abdominal goiter in a 
29-months-old fish. The thyroid mass was round, circumscribed, and measured one by 
one-half cubic centimeter, was attached to the cardiac end of the stomach by a connective 
tissue pedicle and extended into the abdominal cavity. The fish had a large ventral 
tumor histologically identical with the abdominal growth. Because an examination 
of the visceral regions showed no such deposits of thyroid tissue, these authors looked 
upon this specimen as an enlarged aberrant thyroid deposit. They also report having 
seen growths on the tip of the lower jaw in from 2 to 3 per cent of all fish with visible 
tumors examined by them, and these they also hold to have sprung from misplaced 
thyroid deposits. 
COMPARATIVE PATHOLOGY. 
The study of hyperplasia and carcinoma of the thyroid in the Salmonidae, on account 
of the great similarity in the changes in the organ of the fish to that occurring in mam- 
mals, seems likely to throw important light upon the origin of certain structures which 
have been the subject of extensive study in the thyroid of mammals. Virchow (1863), 
Wolfler (1883), Hitzig (1894), and Michaud (1906) have described in the thyroid of 
man small adenomata, the condition being known as struma nodosa. Virchow held 
that these nodules developed by proliferation from the follicles of the thyroid. Wolfler 
held that they developed from misplaced embryonic rests. Hitzig evidently opposed 
the theory of Wolfler as to the embryonic origin of these nodules and held that they 
developed by proliferation from the normal tissue of the thyroid, for the reason that 
in normal thyroids they were never found. Michaud has carefully studied the genesis 
of these adenomata and agrees with Virchow and Hitzig that they are formed by pro- 
liferation from normal structures of the thyroid. 
According to Michaud these growths develop by changes in the epithelium of 
normal follicles, which take on columnar type and through proliferation of the cells form 
extensions and protrusion of the follicles and finally by budding produce -nev/ follicles 
which become detached from the original. The first changes, which are focal, are 
restricted by the surrounding stroma, which takes no part in the change. From this 
point on the nodule grows by proliferation of the structures within it, especially those 
toward the center. The very first evidence of this change is found by Michaud in the 
presence in the thyroid structure of long, tortuous clefts or tubes with cubical or colum- 
nar epithelium, staining more deeply than the surrounding structures, these tubules 
having already been noted and described by Hitzig. From these tubules, by the process 
of budding above described, are developed focal nodules, i. e., struma nodosa. 
It will be seen that the description given by Hitzig and Michaud for the development 
of these isolated adenomata in the mammalian thyroid is exactly like the beginning 
