THE FUNCTIONS OF THE THYROID 485 



(3) All the effects of thyroidectomy are more marked in car- 

 nivorous animals than in herbivora ; indeed, the latter may be 

 able to live in fair condition for several years without a thyroid. 1 

 Administration of meat to thyroidectomized herbivora or omniv- 

 ora causes a great increase in the symptoms, while thyroidec- 

 tomized carnivora do much better if kept without meat. Thus, 

 Blum 2 found that thyroidectomized dogs, which were doing well 

 on a milk diet, developed symptoms of athyreosis immediately 

 they were given meat. This fact has been interpreted as indi- 

 cating that toxic materials are formed from meat in the intes- 

 tinal tract, which under normal conditions are neutralized by 

 the thyroid. In support of this view is the observation of 

 Watson 3 that a pure meat diet causes in fowls a great hyper- 

 trophy of both the thyroid and the parathyroid glands, while in 

 rats hyperplastic changes resembling those of exophthalmic 

 goiter are produced by meat diet. On the other hand, one may 

 well imagine that the so-called autointoxication in athyreosis is 

 not from intestinal putrefaction, but is due to the products of 

 incomplete metabolism of proteids within the tissues, which are 

 destroyed when proteid metabolism is normal, but not when the 

 metabolism-favoring influence of the thyroid is wanting. It 

 should also be added that the presence of specific poisonous 

 substances in the blood or urine of thyroidectomized animals 

 has not been conclusively established. 4 



Relation to Generative Functions. The hypertrophy 

 of the thyroid that occurs at puberty, during menstruation, and 

 especially during lactation, is possibly in response to an auto- 

 intoxication, but far more probably in response to the increased 

 proteid metabolism. In pregnancy and lactation the maternal 

 thyroid functionates for both mother and offspring, the thyroid 

 of the new-born containing either no iodin at all or but the most 

 minute traces. If the greater part of the thyroid is removed 

 from pregnant bitches, the puppies show a great compensatory 

 hypertrophy of the thyroid (Halsted 5 ). 



1 Part of these results may be due to the fact that in some herbivora the 

 parathyroids are so far separated from the thyroid that they are not ordinarily 

 removed in thyroidectomy, whereas in many carnivora complete removal of 

 parathyroids with the thyroids is more likely to be accomplished. 



2 Virchow's Arch., 1900 (162), 375. 



3 Lancet, 1905 (i), 347. 



*Kemedi (Lo Sperimentale, 1902; abst. in Cent. f. Path., 1903 (14), 695) 

 claims that tetanus toxin and other bacterial poisons, when injected into the 

 thyroid gland, are harmless, which he attributes to a neutralization by the 

 colloid. 



5 Johns Hopkins Hosp. Rep., 1896 (1), 373 ; also Edmunds, Trans. London 

 Path. Soc., 1900 (51), 221. 



