377 



These were typical in appearance, rounded, paler in colour than the 

 thyroid and having a separate and distinct blood supply. The animal 

 lived without any symptoms for eighty three days, when a second oper- 

 ation was performed. The two parathyroids which had been left 

 behind were found to have hypertrophied and each of them showed 

 on microscopic examination the appearance depicted in Fig. 1. 





ß 



.J>'<i— 4i,'r - - e. interves. 





— e. ves. 



t^»5 



3- 



Fig. 1. Parathyroid of dog, eighty-three days after thyroidectomy, showing ve- 

 sicles, some of which contain colloid. X 120. c. colloid, e.interves. intervesicular epi- 

 thelial tissue, ves. vesicle, eves, colloid vesicle, e.ves. epithelium lining to vesicles. 



They had to all intents and purposes become converted into 

 thyroid. There was still a comparatively large amount of intervesi- 

 cular tissue which was identical with that of the solid columns forming 

 the normal parathyroid. See Fig, 2. 





— -bld.v. 



^^000^: ^ •••••• 



Fig. 2. Normal parathyroid of dog. X ^-*^- ^•''•'^- ^^^^^^ columns of cells, bld.v. 

 blood vessel. To be compared with Fig. 1. 



