492 BULLETIN OP THE BUREAU OF FISHERIES. 



the thyroid of normal dogs, the remaining portion would become hyperplastic (1896), 

 has recently (1913) repeated these experiments and now finds that when the present-day 

 aseptic methods are employed, especially the careful sterilization of the skin with iodine, 

 no compensatory hypertrophy results. Although not definitely expressing himself as to 

 the cause of the hyperplasia which followed his original experiments, in the light of de 

 Quervain's production of hyperplasia with the products of organisms, above referred to, 

 Halsted recognizes the possibility that the hyperplasia in the older experiments may 

 have been due to infection. 



The experiments of Bircher indicate a very intimate relation between the experi- 

 mental production of struma in rats and dogs and the etiology of tumors of the thyroid. 

 The fact that he has produced nodular struma in rats, that struma nodosa is generally 

 looked upon as the change from which neoplasms of the thyroid in mammals spring, that 

 the other changes of the thyroid in his experimental rats present intensive parenchyma- 

 tous hyperplastic degeneration, makes it clear that perhaps the concentration of the 

 agent causing goiter and the method of its administration, the length of time in which 

 it is permitted to work, or the intensity of its action may determine the character of the 

 early changes of the thyroid in these experiments. The changes in our dogs have appar- 

 ently developed more quickly and more intensely than those in the experiments made by 

 Bircher. This would probably explain why our results have shown such diffuse and 

 intensive changes in the thyroids of our affected dogs. Dog 18, the only adult dog so far 

 exposed to the action of the agent in our experiments, presents outspoken degenerative 

 changes at the center of the gland and evidences of infiltration of the capsule. The 

 period of time covered by Bircher's experiments was much longer than those of our own. 



We have reported briefly on a few experiments with rats, from which it is clear that 

 hyperplastic changes in the thyroid may be induced in rats under conditions similar 

 to those detailed in the experiments with the dogs. There are many other points of 

 similarity between Bircher's experiments and ours. The agent is in both cases destroyed 

 by boiling and it is not readily transported for a great distance. We have been unable 

 to produce changes in the thyroid of rats with water transported from Maine to the 

 institute in Buffalo. Our prompt and best results have, as with Bircher, been obtained 

 by giving the water from the scrapings freshly to the animals on the ground where the 

 agent is produced. We have not yet been able to carry out extensive filtration experi- 

 ments, but have such experiments in progress and hope to report on them later. 



Bircher, in his experiments, has compared the results obtained in the production of 

 experimental struma in rats with the results obtained by de Quervain and argues there- 

 from that the agent of goiter as he finds it in Switzerland is probably a parasitic agent. 

 He finds in filtration experiments with moderately fine Berkefeld bougies that intensive 

 general degenerative changes of the nature of cretinism are produced by the residues 

 scraped from the outside of the filters, and infers that possibly it is the toxic products of 

 an organism which pass through the filter. These toxic products tend to produce struma 

 and the unfilterable portions possibly contain the organism that tends to produce 

 general constitutional disturbances of growth, i. e., cretinism. Our dog 18 showed 

 general nutritional disturbances, loss of weight and strength, staggering gait. To deter- 



