THE PARATHYROIDS 



That the parathyroids, which are four in number in Relationship 

 the human subject and in most mammals, are embryonal t h y ™id and 

 thyroid tissue was first propounded by Gley 1 in 1891, but parathyroids. 

 ten years later he reviewed his work on the subject 2 , 

 and substituted for his original theory of an anatomical 

 relationship between the thyroid and parathyroids the 

 view that the relationship was a functional one. Subse- 

 quently, Vincent and Jolly 3 verified the fact that after 

 removal of the thyroid the parathyroids may develop 

 the structure of true thyroid with colloid formation, and 

 they maintained that the thyroparathyroid apparatus 

 forms one organ, and not two distinct entities ; but, on 

 the other hand, there is a considerable body of evidence 

 to show that the parathyroids have functions different 

 from those of the thyroid, and in this connexion I have 

 already mentioned the dissimilar effects produced by the 

 removal of these organs. However, the functional unity 

 of closely connected parts of apparently double hormono- 

 poietic organs — the pars anterior and posterior of the 

 pituitary, the cortex and medulla of the suprarenals, and 

 the thyroid and parathyroids — is not improbable, in spite 

 of morphological and other reasons which tempt us to 

 hold a contrary opinion. 



In pregnancy there is normally some hyperplasia in The para- 

 the parathyroids, and this is probably connected with the relation to 

 importance in this condition of the calcium metabolism, pregnancy. 

 with which these organs are intimately associated. We 



1 Gley, E., Compt. Rend. Soc. Biol, 1891, vol. iii, p. 843. 



2 Gley, E., Archiv. Ital. de Biol., 1901, vol. xxxvi, p. 57. 



3 Vincent, S., and W. A. Jolly, Journ. Physiol, 1904-5, vol. xxxii, 

 p. 65. 



