Allen: The Thyroid Gland and Hypophysis 



417 



A SAGITTAL SECTION OF THE HYPOPHYSIS (PITUITARY 

 GLAND) OF THE FROG 



Ant. 1 — Anterior lobe. p. int. — Intermediate lobe. n.l. — Posterior 

 lobe (neural lobe), p.t. — Lateral lobe (pars tuberalis). (Fig. 17.) 

 Illustration from The Anatomical Record Vol. XV, No. 2, Sept. 1918. 



the intermediate lobe and the posterior 

 into specimens from which the three 

 lobes mentioned were extirpated. 

 These tissues thus transplanted were 

 taken from adult frogs and transferred 

 to a pocket under the skin above one 

 eye of the tadpole at some distance 

 from the normal position. The results 

 are most striking. The transplanta- 

 tion of the anterior lobe brings about 

 an initial increase in size and a strong 

 tendency toward metamorphosis. Com- 

 plete transformation has not been pro- 

 duced in this manner but there has 

 been a close approach toward it. 

 This lobe has no influence upon the 

 color change, but the restoration of the 

 intermediate lobe into the white pitu- 

 itary-less specimens causes a resump- 

 tion of the normal black color. The 

 influence of the anterior lobe of the 

 hypophysis upon metamorphosis — 

 growing mature — is closely linked with 

 the thyroid gland. In tadpoles from 

 which the hypophysis has been re- 

 moved, the thyroid gland is very 

 poorly developed. A few follicles are 

 formed with very^ small masses of col- 

 loid secretion. Evidently the thyroid 

 gland remains inactive in the absence 

 of the anterior lobe of the hypophysis, 

 the two being most intimately associ- 

 ated in physiological activity. It was 

 stated above that the transplantation 

 of the anterior lobe of a frog hypo- 



P;'"'- .-..-... physis into one of 



these tadpoles de- 

 prived of its hypo- 

 physis causes a 

 resumption of de- 

 velopment. It is 

 most significant 

 that this accom- 

 panies a marked 

 increase in the size 

 of the thyroid gland 

 and of its con- 

 tained colloid 

 secretion. The res- 

 toration of the 

 anterior lobe of the 

 hypophysis thus 

 causes a resump- 

 tion of the growth 

 and functional ac- 

 tivity of the 

 thyroid, and the tadpole proceeds on 

 its way toward metamorphosis. 



Smith has shown that feeding the 

 anterior lobe of beef hypophysis to 

 tadpoles of Rana boyeli from which 

 the hypophysis had been removed, 

 causes them to resume their normal 

 rate of size growth that had been 

 inhibited by its absence. Hoskins 

 claimed that the feeding of commercial 

 hypophysis preparations also produces 

 metamorphosis, but Smith has shown 

 that this is not the case where he him- 

 self secured and prepared his material. 

 Hoskins had analyzed the commercial 

 preparation that he used and demon- 

 strated a small quantity of iodine 

 which he considered too little to pro- 

 duce an effect. The presence of this 

 iodine was probably due to contamina- 

 tion and the amount was, contrary to 

 Hoskins' judgment, sufficient to pro- 

 duce the metamorphosis that he ob- 

 served. The writer also produced 

 partial transformation with commercial 

 preparations in unpublished experi- 

 ments performed five years ago, but 

 hesitated to publish the result because 

 of doubt regarding the purity of the 

 preparation. We are thus forced to 

 conclude that the feeding of laboratory 

 prepared anterior lobe of the hypo- 

 physis, free from iodine or possible 

 thyroid contamination, does not bring 



