488 
bulletin of the bureau of fisheries. 
The puppy (dog 21) presents a thyroid structure which may be considered normal 
for a young dog. The alveoli are less spherical and oval, varying in size, filled with 
stainable colloid. The epithelium is flattened. There are some areas in the thyroid 
structure in which a slight tendency to budding of the epithelium with a change to 
columnar may be observed and there are some areas in which there appears to be a 
somewhat richer stroma than usual. It is, however, only an increase in amount of 
connective tissue without any evidence of changes in staining characteristics of the 
cells. As this puppy received pond- 10 mud and water for several months previous to 
the final experiment, it is possible that the very slight changes here noted may be evi- 
dence of the first beginnings of a change induced during that period. Diagnosis : Normal 
thyroid of puppy. (Fig. no.) 
Section of the left lobe of the thyroid of dog 20 shows follicles of varying size, the 
oval and spherical type predominating, but some follicles in which there is evidence of 
beginning bud formation. The lining epithelium of the more simple follicles is flat. 
The follicles are filled with stainable colloid. In the somewhat more irregular follicles 
the epithelium forming the budlike projections into the alveoli is cubical. The nuclei 
are stained deeply and are spherical or oval. The details of the nuclei can not be made 
out. Intensely stained. There is some slight thickening of the septa here and there 
through the thyroid tissue. No evidence of hyperemia, no other change except the 
slight budding. (Fig. 114.) The thyroid tissue is mostly normal for a young dog; 
slight evidences indicating the beginning of hyperplasia. As this dog had previously 
received pond- 10 mud and water, as had dog 21, slight evidences of hyperplasia may 
be due to this previous stage of the experiment. Diagnosis: Areas of slight hyperplasia. 
In the same way and beginning at the same time (Aug. i ) as in the preceding exper- 
iment, a young bull terrier (dog 18) was given to drink water in which was suspended 
scrapings from another and old fish trough (no. 9 of old hatchery). The water, 
however, was kept in the kennel and the dog allowed to drink at will. The tempera- 
ture varied with the weather. In the winter the room was heated somewhat to prevent 
freezing, but seldom rose above 45° F., and was often near the freezing point. The 
control was dog 19, which received the scrapings water after boiling. Neither had 
thyroid enlargement at the beginning of the experiment. The food was liver and dog 
biscuit for both. The bull terrier, after receiving for six months water from the pail in 
which were suspended the scrapings, showed a marked emaciation, muscular weakness, 
and a staggering gait. The thyroid was readily palpable. The dog was killed and 
both lobes found distinctly enlarged, the left lobe being about one-quarter larger than 
the right and measuring 54 by 28 by 26 millimeters, and both very vascular. 
Under the microscope the thyroid gland shows extensive pathological change. 
The tissue is for the most part made up of a solid adenomatous structure with irregular 
and narrow spaces representing preexisting vesicles. Under low power whole fields of 
almost solid compact adenomatous tissue are found. In the irregular clefts and spaces 
in the more open portions of the tissue, complex and marked papillary processes covered 
with high columnar epithelium characterize the tissue. This change may be said to 
be more constant in the peripheral portions of the section of the thyroid tissue. (Fig. 
