THYROID AND PARATHYROIDS 



231 



)( 



r/7y/n. /// 



_ Fost. branch. 

 rAym./V f)Q(/y 



X 



Thyro/cf 



Fig. 30. — Origin of thyroid, parathyroids and thymus in the mammahan 

 ■ embryo. I, ii, ill, iv, branchial i>ouches. The post-branchial 

 body in mammals either disappears or becomes incorporated with 

 the thyroid (from Schafer, The Endocrine Organs). 



