On the other hand, meat-eating animals are more sensitive to excision of the thyroid body than are grain eaters.[45] Chemical studies have shown that the thyroid is concerned in basal metabolism since this is increased in hyperthyroidism and decreased in myxedema; nitrogen output is much elevated. Thyroid physiology stands probably in some relation to the cardiac mechanism since in simple colloid or simple hyperplastic goitre if of long duration, cardiac enlargement and disease may be greater than the excess work occasioned by the mere physical bulk of the enlarged gland in the neck would seem to warrant. A detoxicating function has been ascribed to the gland, but Murray discredits this on the ground that congestion occurs in infectious disease of warm blooded animals but not in snakes. He thinks the gland more likely stands in some connection with the thermoregulatory mechanism. It is evident from the foregoing that the thyroid is closely related to protein metabolism, and that this is in some way connected with the ability the body possesses to use iodine in the food if it can get it. Feeding of meat to fish was found by Marine to increase the size of the thyroid. With all this in mind it is not astonishing that two-thirds of our cases of thyroid abnormalities were found in the order Carnivora. The anatomical changes of the human thyroid that precede or accompany the various clinical pictures cannot be said to be uniform to a degree that one can even approximately predict in every case what will be found at operation, at autopsy or by the microscope. Furthermore, much discussion has existed upon the importance of the several changes, the association with clinical phenomena and the nomenclature. I shall not enter the academic discussion with our material because so much has depended, in human medicine, upon symptoms, signs and chemistry—data that we cannot adduce. Upon many occasions I have seen animals with very evident goitres, but have not been able to detect bulging of the eyes or especial nervousness. One striped hyena carried his mass for several years. It swelled up occasionally and seemed to cause dyspnœa. At one examination of the beast, to see if anything could be done for him, a large cyst broke under the examining hand, whereupon a deep inspiration was heard and relief was apparent. This handling was repeated twice, these times with the purpose of breaking cysts and when this was successful disappearance of the dyspnœa was observed. However, a similar attempt upon another hyena and a wolf failed possibly because no large thin-walled cyst was present. These and the case of the lion cub (page 170) are the only instances in which the enlarged thyroid seemed to have given serious difficulty, and the symptoms were probably due to pressure. Many, indeed most, enlarged thyroids have been found at autopsy, when the Garden personnel was unaware of their existence. Interesting notes of familial cretinism will be found under the