488 BULLETIN OP 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 

 cormective 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. 110.) 



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 e\'idence 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 3'oung 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 si.x 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. 



