EFFECT OF EXTIRPATION OF THYROID 597 



metamorphosing normal tadpoles. This shows that the pitui- 

 tary gland of the thyroidless specimen has made a marked in- 

 crease over the normal pituitary gland. The portion of the 

 pituitary glands in question is the anterior lobe. Thyroidless 

 tadpole 5 (table 2), with a body length of 16.2 mm. was abnor- 

 mally small. The pituitary gland was smaller than that of the 

 September 25 (table 2, no. 4) thyroidless specimen. When the 

 pituitary gland of this specimen is considered with body length 

 correction as were the glands of the control and the thjToidless 

 tadpoles it has a relative size of 254. Even in this small thyroid- 

 less tadpole the pituitary gland is proportionally larger than in 

 the control tadpoles. 



The thymus gland of the tadpole killed September 25 (no. 4, 

 table 2), had a relative volume with body length correction of 

 248. The thymus glands of the control tadpoles were much 

 larger and the average for the class was 1293. This shows that 

 during the period of metamorphosis the thymus gland is in- 

 creased very much. The thymus gland of the control tadpole 

 is therefore much larger than that of the thyroidless tadpole 

 which is slightly older. 



The striking thing shown in this stage is that the pituitary 

 gland of the thyroidless tadpole is much larger than that of the 

 control tadpoles while the thymus glands of the latter are a great 

 deal larger than those of the thyroidless tadpole. These dif- 

 ferences are clearly shown on the graphs. The average size' 

 of the pituitary gland in recently metamorphosed frogs was 

 represented by 138. This shows that the pituitary gland is 

 smaller than in the thyroidless tadpole killed September 25 

 (table 2 and chart 1). 



The average size of the thymus glands in recently metamor- 

 phosed frogs was represented by 608, (table 2). The thymus 

 gland of the thyroidless tadpole killed September 25 (table 2, 

 no. 4), two months later had a value of 248. This shows that 

 the recently metamorphosed frog has larger glands than the 

 thyroidless tadpole killed September 25; but smaller than those 

 of normal tadpoles during metamorphosis (table 2 and chart 2). 



