THE THYROID GLAND AND ITS DISEASES 235 



In 1896 7 E. H. Cunningham contributed a masterly article entitled 

 "Experimental Thyroidism." In this will be found a full and very 

 interesting account of the history of the subject up to that date. In 

 Cunningham's work, and indeed in that of all subsequent investigators in 

 this section of the subject, the question under discussion has been : "Can 

 we induce symptoms of exophthalmic goiter by administering thyroid 

 substance to animals?" Cunningham found, as the most trustworthy 

 recent observers have found, that we cannot. Such symptoms as were 

 noted, he attributed to an intoxication resulting from the ingestion of 

 decomposed thyroid material. Moreover, similar effects could be obtained 

 by treatment with other tissues. In his conclusions Cunningham states: 

 "The effects resulting from the intravascular or subcutaneous injections 

 of aqueous extracts, decoctions and the concentrated extractives of the 

 thyroid tissue, of the thymus, of muscle, etc., are by no means necessarily 

 indicative of the function and the action of the hypothetical internal 

 secretions of the same tissues during .life." This is a lesson which many 

 modern writers on internal secretion have still to learn. 8 , 



Among those who claim that they have succeeded in inducing symptoms 

 of hyperthyroidism in animals by thyroid feeding is Walter Edmunds. He 

 employed "thyro-colloid" made from the thyroid glands of sheep by a 

 process devised by E. Hutchison. In monkeys "well-marked symptoms 

 were produced namely, proptosis, dilatation of pupils, widening of 

 palpebral fissures, erection of hairs on the head, the hair falling out in 

 patches, paralysis of one or more limbs, emaciation and muscular weak- 

 ness, and finally death from asthenia." There is no record that Edmunds 

 carried out any control experiments. He gives sketches of a monkey 

 before and after treatment. 



In animals then, the results of experiments are differently interpreted 

 by different observers and the actual symptoms found are variously 

 stated. There seem to be few well authenticated cases in which the con- 

 dition even strongly suggested that of exophthalmic goiter. 



Carlson, Eooks and McKie have recently reached the conclusion that 

 toxic symptoms can in all probability be produced in all animals by 

 thyroid feeding. Some groups of animals are much more resistant than 

 others. To what they owe their resistance is not clear. In the more 

 resistant groups the symptoms are probably not specific thyroid effects, 

 but complicated by the effects of the excessive protein diet. This applies 



7 Not published until 1898. 



8 There are, of course, many points in Cunningham's paper which would neces- 

 sarily be stated very differently at the present day, but the chief doctrines and the 

 general trend of the communication are in my opinion in accord with those of the 



'most careful examples of recent work, various clinical writers to the contrary not- 

 withstanding. Just as in the extirpation experiments there has been a tendency to 

 find "myxedema" on very slight provocation, so in feeding investigations observers 

 have rushed too soon to the conclusion that the symptoms they noted were those of 

 exophthalmic goiter. 



