CARCINOMA OF THE THYROID IN SAEMONOID FISHES. 
413 
inches in length and in its rather emaciated condition weighed 4 pounds. A salmon of 
this length in health should weigh 6 to 8 pounds. A large thyroid tumor involved the 
whole gill region, vegetating in the floor of the mouth and presenting on the ventral 
surface several cystic lobes which kept the gills and gill covers well distended. (Fig. 72.) 
Sebago Lake is located in the southwestern part of Maine. It has an area of about 
45 square miles and a general depth of 316 feet. It has but few shoal places, the depth 
of water often reaching close to the shores, which are for the most part rocky, save in 
a few shallow coves. The lake has little aquatic vegetation; the water is regarded 
as unquestionably pure and is the source of supply for the city of Portland. While the 
fish had been living in a wild state for two or three years, it was originally planted from 
a fish hatchery, where it may have contracted the disease. Microscopic inspection 
of this tumor (see fig. 75) shows it to be almost entirely of the alveolar type, showing 
at the center areas of cystic colloid degeneration. 
These four tumor-bearing fish were living under wild natural conditions when 
taken. All can be related more or less remotely to fish culture. They were taken from 
waters in inhabited regions, in which fish culture has been practiced for years, and these 
waters had frequently received the products of hatcheries. The trout inhabited a stocked 
stream, and was possibly the product of a hatchery and fed artificially, or was descended 
from fish so treated. The landlocked salmon was probably planted from a hatchery. No 
whitefish are fed artificially nor reared to maturity in domestication. The product of 
their artificial propagation is planted soon after hatching. The most that may be said, 
therefore, as far as the relation of this tumor-bearing whitefish to domestication is con- 
cerned, is that it may have been artificially hatched, planted before feeding, and was 
living in a large lake which received the drainage from a large trout hatchery and breed- 
ing establishment at which the thyroid disease was endemic and epidemic. It was taken 
within 5 miles of the point of entry of this drainage inflow. 
In one of the small lakes of the Adirondack Mountains of New York, which have 
been stocked with trout from hatcheries, anglers occasionally report the taking of fish 
with visible tumors at the throat. 
In Europe Hofer (1904, p. 194) reports the disease in wild lake trout {Trutla lacus- 
tris) living in the Mondsee. Dr. Plehn informs us that occasionally trout with thyroid 
tumors and living under wild conditions in the streams of Bavaria are sent to the 
Bavarian Fisheries Biological Station for examination. 
OCCURFIENCE AND COURSE OF THE DISEASE UNDER DOMESTICATION 
DISTRIBUTION OF THE DISEASE IN UNITED STATES HATCHERIES. 
The thyroid tumor among fishes is undoubtedly of wide distribution. We believe 
it occurs almost universally where trout are made the subject of artificial propagation 
and rearing under the ordinary conditions of fish culture in the United States. A 
complete canvass of all the trout-breeding establishments in the country has not yet 
been made, but such an investigation would beyond question indicate the distribution 
of the disease as coextensive with trout culture. The following list gives the places 
60289° — Bull. 32 — 14 27 
