THE THYROID GLAND AND ITS DISEASES 211 



be detected chemically in the gland. According to Kummer, the iodin 

 increases in amount to thirty years of age and decreases after forty. It 

 is to be noted that the colloid in the hypophysis is also a very late develop- 

 ment. 



T 



Fig. 3. Scheme of the development of the human thyroid gland, after Norris. 



Ultimobranchial Bodies. In young embryos certain structures arise 

 from the fifth or last gill pouches, called for this reason "ultimobranchial 

 bodies," which constitute in part the lateral thyroids of lower forms. 



