CARCINOMA OF THE THYROID IN SALMONOID FISHES. 459 



In the small brook about 100 yards in length wooden divisions and tank-like arrange- 

 ments had been constructed. In these the young fish were placed and all the fish both 

 in the old concrete tanks and in the spring were fed with chopped raw beef liver and 

 ox heart muscle. An examination of specimens taken from the two sources in the 

 autumn of 191 1, of fish respectively 6 and 18 months old, taken from both sources, 

 showed that whereas the fish in the old concrete ponds had well-defined hyperplasia 

 (fig. 93), those kept in the spring water had thyroids exactly like those found in wild 

 fish (fig. 94), although both had been liberally fed upon raw liver and ox heart. From 

 this observation we must conclude that the selective feeding experiments at Craig 

 Brook station indicate that the feeding of raw ox heart and liver produce conditions 

 either in the tanks or in the fish themselves which favor the development of the disease, 

 but that such feeding of raw heart muscle and liver is not the direct cause of the disease. 

 It is hard to understand why fish fed upon cooked liver should have resisted the disease 

 so much longer than those fed upon the uncooked liver, unless it is possible that the 

 agent causing the disease is sometimes or usually transmitted with the uncooked 

 materials, or that cooking the material delays decomposition and thus favors a more 

 hygienic condition in the tanks. The complete resistance of fish fed upon natural 

 food, chopped marine fish, and vegetable food, all of vvhich were obtained from sources 

 entirely different from either the heart muscle or liver, would rather suggest that these 

 sources of food are free from the possible contamination with the agent of the disease; 

 or, again, that they are not so easily decomposed in the tanks and do not therefore 

 contribute to a favorable condition for the propagation or development of the agent 

 in the tanks. 



McCarrison (1906) points out that in Chitral where goiter is endemic the people 

 are for the most part poor. Food is plentiful, comparatively speaking, from July to 

 February, after which the people are obliged to live on the poorest grains, dried fruits, 

 and the green stuffs of the spring. Their food is entirely vegetable. Flesh meat is an 

 article of diet far beyond their means, while salt is a luxury to all except the richest 

 families. 



That the disease may be introduced into a community where it has not previously 

 been and that in such cases the water supply becomes at once the suspected agent of 

 distribution is shown by McCarrison's remarkable observation in Nagar. 



In the village of Nagar goiter was unknown six years ago. Nagar is a small State situated up one 

 of the many side valleys on the left bank of the Gilgit River. It will be remembered as the scene of a 

 smart frontier rising in 1893. It was after this year that the little State of Nagar began to be opened up; 

 previously, jealous of its independence and at war with its immediate neighbors, it was careful to 

 exclude foreigners. During recent years intercourse with the outside world has become more free, 

 but still there is a decided prejudice against the settling of foreigners in this little hill State. 



Some five years ago certain cases of goiter were introduced from without, and since then the disease 

 has begun to gain a footing. It may be as well to indicate clearly that there can be no doubt about 

 the fact that goiter was quite unknown six years ago. The fact that it has gained a footing in his territory 

 is a matter of very considerable anxiety to the present rajah, and through his help I was enabled to go 

 into the matter with great care. All the important men of the State, the rajah himself, councilors, 

 priests, etc., assure me that no case of goiter ever originated in Nagar till within the last six years. 



