GOITER STRUM A BRONCHOCELE 343 



the age of the animal, should make the differentiation from 

 other forms of goiter comparatively easy. 



Prognosis. Unfavorable. 



Treatment. But little can be expected of treatment. In 

 the early stages, before involvement of the adjacent tissues 

 takes place, extirpation of the gland may relieve the condition 

 for a time but no permanent results can be hoped for. 



Exophthalmic Goiter. Basedow's Disease. Graves' s Dis- 

 ease. Definition. A disease characterized by exophthalmos, 

 functional disturbances of the circulatory system, and more 

 or less enlargement of the thyroid gland. This disease is 

 not of frequent occurrence in animals, but is found occa- 

 sionally in the dog. 



Etiology. The exact etiological factor has been in dispute, 

 but is evidently a pure neurosis as indicated by some of the 

 more recent investigations made. It has also been claimed 

 that it is due to a central lesion in the medulla oblongata. 

 A certain amount of evidence has been produced to partially 

 substantiate this claim. The fact that the primary result 

 of the disease is a hyperthyrea would indicate that it 

 might be a special involvement of the glands. However, this 

 has not been proved and the best evidence seems to prove 

 the former etiological factor the most likely. 



Pathology. On examination the thyroid glands show en- 

 largement, congestion, the production of newly formed 

 tubular spaces and a collection of mucinous fluid. They 

 show every evidence of hyperactivity. 



Pathogenesis. It is quite important from every standpoint 

 to note that this form of goiter is a primary hyperthyrea 

 while most forms are just the opposite (athyrea). The 

 development of the disease is the result of the increased 

 secretion of the thyroid glands leading to a general toxic 

 condition. The iodothyroidin content of the secretion is 

 greatly increased which no doubt accounts for the intoxica- 

 tion. 



From an experimental standpoint much the same condition 

 can be produced in animals by administering large and con- 

 tinued doses of thyroid extract. Further, when thyroid 

 extract or iodin is administered in exophthalmic goiter the 

 condition becomes rapidly aggravated. 



