490 BULLETIN OF THE BUREAU OF FISHERIES. 



in size and form. At the center of the lobule where the degenerative changes are most 

 outspoken are found large areas of desquamated cells with cloudy protoplasm, taking 

 the stain deeply. The cell boundaries are not sharply defined, the nuclei generally 

 smaller than in the preceding area, of varying size and deeply stained. Diagnosis: 

 Diffuse hyperplasia of the thyroid gland with degenerative changes at the center and 

 invasion of the capsule at the periphery. 



RATS. 



In 1910 and 1911 a prolonged attempt was made to affect the thyroid of rats by 

 giving them water to drink from the fish ponds in which the disease was endemic. A 

 barrel of water from pond 10 of the Craig Brook station and a quantity of mud from 

 the same pond were shipped to Buffalo and kept in cold storage. A series of experi- 

 ments were begun with young rats obtained from Granby, Mass. Each experimental 

 lot consisted of 10 rats. The food was a mixture of corn, oats, sunflower seeds, and 

 dog biscuit. The mud and water was administered daily to the separate lots as follows: 



1. Trout-pond mud; small quantities. 



2. Trout-pond mud; large quantities. 



3. Trout-pond water. 



4. Craig Brook water. 



5. Trout-pond mud ; cooked. 



6. Trout-pond water; boiled. 



7. Trout-pond water, injected subcutaneously, followed by mud and water feeding. 

 The feeding of the mud, water, etc., was continued with the same individuals for 



a period of about six months. A few were killed from time to time during this period 

 for examination of the thyroid. Neither in these nor in those remaining at the close of 

 the experiment were there any thyroid enlargements or any microscopic condition differ- 

 ing materially from the controls. 



In the light of Bircher's subsequent observations there are several reasons why 

 these experiments might have failed. Bircher gives the following reasons why water 

 may lose its goiter-producing qualities : (a) Water kept under conditions different from 

 those of its origin for days or weeks; (6) water which before use has been continually 

 shaken or has undergone a long trip by rail; (c) water to which small amounts of chem- 

 ical agents have been added ; (d) that the agent is more active in the water in the sum- 

 mer months and that the source frequently loses its activity in the winter.^ Three of 

 these reasons bear on the possible negative nature of the above experiments, and as they 

 are all made with water taken from ponds in which the agent is present in dilute form, 

 it is quite clear that the length of time was not sufficiently great to produce positive 

 results. These experiments must therefore be repeated with the animals at the source of 

 water supply and continued over a period not less than 18 months. 



The pond water and mud having failed to produce definite changes in rats during 

 six months under the experimental conditions, a quantity of scrapings from one of the 

 wooden fish troughs (no. 102), in which thyroid tumors were constantly developed, was 



