926 E. G. HOSKINS 



tomy, were found to be degenerated, the parenchyma being largely replaced 

 by connective tissue. In view of the fact that the thymus is particularly 

 liable to atrophy in any condition involving malnutrition, it is impossible 

 to determine from such observations whether the thyroidectomy as such 

 conditions depression of thymus weight, or whether this latter represents 

 merely one phase of impaired nutrition. E. R. and M. M. Hoskins (1919) 

 noted in a large series of thyroidectomized tadpoles that the thymus gland 

 persists and becomes relatively large. Since such tadpoles grow rapidly 

 and ultimately become two or three times as large as the controls, it is 

 possible to ascribe the thymus enlargement merely to the nutritional factor. 



From the available evidence, no final decision can be .drawn as to the 

 existence of a definite relationship between the thyroid and thymus glands. 

 That the two may be simultaneously affected under various conditions is 

 fairly well demonstrated, but whether either plays a causal role in the 

 changes of the other is unknown. 



Relation between Thyroid and Pancreas. That the thyroid has 

 some relation to carbohydrate metabolism, and that the pancreas has an 

 intimate relation with it, is well known. A decade ago much was heard 

 of Falta's theory that the suprarenals, the pancreas, and the thyroid stand 

 in a close triangular relationship. It was assumed, upon quite inadequate 

 grounds, that the thyroid facilitates the mobilization of dextrose by ex- 

 ercising an inhibitory influence upon the pancreas. Later observations 

 by Underhill and Hillditch (1909) and others, however, have failed to 

 bear out Falta's theory. McCurdy (1909) and others have shown that thy- 

 roidectomy raises the assimilation limit for dextrose. 



Falta (1909) reported that in a single case, after thyroidectomy, an 

 undoubted hypertrophy of the islands of Langerhans was found. Kojima 

 (1916) and Hoshimoto (1920) have found that thyroid feeding results 

 in hypertrophy of the pancreas. 



In view of the highly complicated physiology of carbohydrate metab- 

 olism and of the profound effect which the thyroid has upon metabolism 

 in general, no conclusion is justified from data now available as to whether 

 the thyroid gland has any direct influence upon the pancreas as an en- 

 dccrin organ. 



Relation between Thyroid and Parathyroid Glands. In his earlier 

 studies on the parathyroid glands, Gley noted, following the removal of 

 the thyroid arid the internal parathyroid glands, the external parathyroids 

 hypertrophied and assumed an appearance somewhat similar to that of the 

 thyroid. He concluded, therefore, that under such circumstances the para- 

 thyroid may assume the thyroid functions. Later, however, after further 

 experimentation he discarded this view. Vincent and Jolly (1905) also 

 found, on microscopical examination of the parathyroids left behind after 

 the removal of the thyroid gland, an appearance simulating that of the 

 latter gland. Similar results were obtained by Halpenny and Thompson 



