Section IV, 1917 I1211 Trans. R.S.C 



The Relationship between Thyroid and Parathyroid. 



By J. S. Arnason and Swale Vincent. 



{From the Physiological Laboratory, University of Manitoba, Winnipeg) 

 (Read May Meeting, 1917.) 



The history of this subject up to the year 1912 has been given 

 by Vincent^ and up to 1913 by Biedl.^ 



Vincent and Jolly ,^, * reported that in the cat extirpation of the 

 thyroid gave rise to alterations in the parathyroid which had been 

 left behind. The parathyroid approximated in structure to thyroid. 

 Similar changes after thyroidectomy were found by Halpenny and 

 Thompson^ in the parathyroid of a dog. 



These results have not generally been accepted, and it was thought 

 desirable to carry out a systematic reinvestigation of the subject upon 

 rabbits. In these animals the external parathyroid is situated at 

 some distance from the thyroid lobe. It is therefore easy to remove 

 the thyroid with both internal parathyroids, leaving behind the ex- 

 ternal glandules. We have employed rabbits of different ages and the 

 animals have been kept under the best conditions after the operation 

 for periods varying from seven to one hundred and five days. In all 

 cases the parathyroids were found to be considerably hypertrophied, 

 but in none have we found any trace of vesicle formation. It is 

 possible that there are changes of other kinds and of less significance 

 in the glandules which have been left behind. 



This series of experiments, then, does not lend support to the view 

 that parathyroids left behind after thyroidectomy become converted 

 into thyroid tissue. It is also possible that the anatomical differences 

 between rabbits on one hand and dogs and cats on the other involve 

 also a difference in regard to the potentiality of a change from parathy- 

 roid to thyroid tissue. Notwithstanding the fact that negative 

 results in such cases are of less value than positive ones, we must 

 confess that these experiments have led us to suspect the possibility 

 that there were some errors of observation in the cases reported by 

 Vincent and Jolly ,^,* Halpenny and Thompson,^ and Halpenny.^ It 



1 Vincent. S. Internal Secretion and the Ductless Glands, London, 1912. 



^ Biedl, A. Innere Sekretion, etc., 2nd anfl, Berlin, 1913. 



3 Vincent, S., and Jolly, W. A., Journ. of Physiol., 1904, p. 32. 



♦ Vincent. S., and Jolly., W. A., Journ of Physiol., 1906, XXXIV., p. 295. 



6 Halpenny, J., and Thompson, F. D., Anat. Anz., 1909, XXIV., p. 376. 



•Halpenny, J., Surgery, Gynaecology and Obstetrics, Chicago, 1910. 



