SECRETION. 269 



thyroidectomy, but these cases are rare and may be explained probably by 

 the presence of accessory thyroids which remain after the operation. It has 

 been observed, too, that the operation is more rapidly and certainly fatal in 

 young animals than in old ones. In the monkey as well as in man the evil 

 results following the removal of the glands develop more slowly than in the 

 lower animals, and give rise to a series of symptoms resembling those of 

 myxcedema in man. Among these symptoms may be mentioned a pronounced 

 anaemia, diminution of muscular strength, failure of the mental powers, abnor- 

 mal dryness of the skin, loss of hairs, and a peculiar swelling of the subcu- 

 taneous connective tissue. Physiologists have shown that in the case of dogs 

 the fatal results following thyroidectomy may be mitigated or entirely obviated 

 by grafting a portion of the gland under the skin or in the peritoneal cavity. 

 If the piece grafted is sufficiently large, the animal recovers apparently com- 

 pletely from the operation. So also in removing the thyroids, if a small 

 portion of the gland, or the parathyroids, be left undisturbed the fatal symp- 

 toms do not develop. In human beings suffering from myxoedema as the 

 result of loss of function of the thyroids it has been abundantly shown that 

 injection of thyroid extracts, or feeding the fresh gland, restores the indi- 

 vidual to an approximately normal condition. In the earlier experiments on 

 thyroidectomy no distinction was made between the effects of removal of the 

 thyroids and parathyroids, although, as said above, it was noticed that in 

 some animals a fatal result failed to follow the operation unless care was 

 taken to extirpate the parathyroids as well as the thyroids. It was supposed 

 by some that the parathyroids represented an immature or embryonic form 

 of thyroid tissue, and that after the removal of the thyroids the parathyroids 

 took on their function and assumed a thyroid structure. Histological evi- 

 dence seemed to favor this view, but the latest physiological experiments, on 

 the contrary, have indicated that the parathyroids are not to be regarded as 

 immature structures, but as bodies possessing a definite functional value, dis- 

 tinct from, but not less important than, that of the thyroids themselves. 

 Moussou, 1 whose work has been confirmed in part by others, 2 makes the fol- 

 lowing distinction in regard to the effect of extirpation of these bodies. 

 Removal of the thyroids and accessory thyroids is followed by a slowly 

 developing general trophic disturbance, a progressive cachexia that produces 

 a condition resembling myxcedema. Tn young animals the effect is more 

 marked and causes a condition of cretinism. The animals, therefore, may 

 survive complete thyroidectomy, for long periods at least. Removal of all 

 the parathyroids, on the contrary, is followed by acute disturbances and rapid 

 death, the Symptoms being the same as those formerly described as resulting 

 from complete thyroidectomy. It would seem from these results that both 

 the thyroids and the parathyroids play an important part in the general 

 metabolism of the body. 



1 Proceedings of Fourth International Physiological Congress, Cambridge, 1S98. 

 -<;icy: Archiv fur die gesammte Physiologie, 1897, Bd. lxvi. S. :>08. 



