320 Kojima 



diminished in number. Herring (5) found that thj'roidectomy causes en- 

 largement of the cells of the pars intermedia, which stain more deeply than 

 usual ; in addition, the hyaline masses which occur in the pars nervosa are 

 increased in amount. These changes are described in dogs, cats, and rabbits. 



It must, however, be borne in mind that most experiments on the sub- 

 ject have been carried out without consideration of the fact that the para- 

 thyroids were generally included in the operation. To investigate the 

 inlluence of these, Cimoroni (6) performed total parathyroidectomy leaving 

 the thyroid, and found that the pituitary body showed no changes ; the 

 dogs upon which he operated died, however, rather soon after the operation. 

 Cimoroni also performed thyroidectomy alone upon a number of dogs, 

 taking especial care to preserve the parathyroids. The animals survived 

 for a considerable time after the operation, and he then found changes in 

 the pituitary body similar to those which had already been described by 

 other authors. He obtained similar results in rabbits. Harvier's (7) 

 experiments confirm those of Cimoroni. It would appear therefore that 

 it is the thyroidectomy and not the parathyroidectomy which plays the 

 more important part in effecting the changes which had been noticed in 

 the pituitary after removal of both thyroid and parathyroid. 



Incidentally it may be remarked that if a part only of the thyroid be 

 removed the rest enlarges and its epithelium undergoes proliferation (see 

 succeeding paper). This compensatory growth of the remainder of the 

 thyroid Avas noticed by Rogowitsch, and later by Gley and Nicolas (8), 

 Horsley (9), Halsted (10), Edmunds (11), and Murray (12). Accord- 

 ing to Halsted it is sufficient to prevent symptoms of athyroidism, even 

 if only one-sixteenth of the original gland is left. 



Parathyroidectomy. — Regarding the parathyroids, Vassale and 

 Generali (13), Moussu (1-i), Erdheim (15), Rouxeau (16), and others 

 have found that although total parathyroidectomy in most animals pro- 

 duces fatal symptoms of tetany, if two of the parathj^roids are left there 

 are usually no symptoms at all. If, however, three are removed, serious 

 symptoms appear, although deferred. According to Alquier (17), 

 Rouxeau, Harvier, Gley (IS), Haberfeld and Schilder (19), after 

 partial parathyroidectomy the remaining parathyroid undergoes hyper- 

 trophy, the gland becoming heavier than normal. According to Pepere 

 (20) and Vassale and Generali there is no cell proliferation, nor is there 

 any obvious change in the structure of the cells, but a large amount of 

 colloid accumulates in the lymph interstices of the gland and there is a 

 tendency to the formation of vesicles in it. Haberfeld and Schilder 

 state that no histological changes occur in the remaining parathyroid other 

 than simple enlargement. 



Castration. — Fischera (21) was the first to notice in several species 

 of animals (burfalo, bull, guinea-pig, rabbit, cock) that after castration 

 the pituitary body enlarges to about twice its normal size and weight. He 

 does not, however, state the body-weights of the animals operated upon. 



