THE THYROID 19 



hearing entirely absent ; no reactions of the eyelids 

 to sounds." 



If now there still remains some question as to 

 the soundness of the diagnosis, all doubts are im- 

 mediately removed by prescribing extracts of the 

 thyroid gland to the young sufferer. The recovery 

 as a consequence is little short of miraculous. 



Thyroid feeding and the development of frogs. 

 In his fascinating article on "Natural Death and 

 the Duration of Life" (Scientific Monthly, Decem- 

 ber, 1919), Professor Jacques Loeb describes the 

 remarkable effect of thyroid feeding on the devel- 

 opment of the frog and salamander. He writes: 

 "It is possible that some of the changes underlying 

 metamorphosis are due to changes in the circula- 

 tion of the blood. Gudernatsch made the remark- 

 able discovery that this metamorphosis, which in 

 our climate usually occurs during the third or 

 fourth month of the life of the tadpole, can be 

 brought about at will even in the youngest tadpoles 

 by feeding them with thyroid gland, no matter from 

 which animal. By feeding very young tadpoles 

 with this substance, frogs not larger than a fly 

 could be produced. Allen added the observation 

 that if a young tadpole is deprived of its thyroid 

 gland, it is unable ever to become a frog ; and that 

 it remains a tadpole which can reach, however, a 

 long life and continue to grow beyond the usual size 



