THE PAEATHYBOID GLANDS 555 



lieved to be embryonic thyroids capable of developing into functionally 

 active tissue, so that really all the effects were due to the loss of the 

 thyroids. 



After the discovery of the internal parathyroids by Kohn, the embry- 

 onic character of the parathyroids was rejected by most, but still advo- 

 cated by a few, and it was taught that they were separate and independent 

 organs, functionally and embryologically, and had only an anatomical re- 

 lationship to the thyroid. In thyroparathyroidectomy their absence was 

 alone responsible for the acute neuromuscular symptoms. Failure to ob- 

 tain these in any experimental animal was ascribed to their incomplete 

 removal, or to the presence of accessory parathyroids inadvertently left 

 behind. 



Functionally, the parathyroid glands were believed to regulate calcium 

 metabolism; interference with this led to a depletion of calcium in the 

 tissues and, as a consequence, to hyperexcitability of the nervous system. 



Failure of this theory to account for many experimentally determined 

 facts led to its abandonment by most, in favor of the Guanidin Intoxication 

 Theory, which by many is at present held to explain the symptoms of para- 

 thyroidectomy in animals and idiopathic tetany in the human subject. 

 Both conditions are believed to be practically identical and to be due to 

 absence or depression of the parathyroid function. 



In the preparation of this article, in addition to the references specifi- 

 cally given, the following monographs have been consulted: "The Endo- 

 crine Organs," by Sir Edward S. Schafer, London, 1916; "Internal Se- 

 cretion and the Ductless Glands," by Swale Vincent, London, 1912 ; 

 "Surgery and Pathology of the Thyroid and Parathyroid Glands," by 

 Ochsner and Thompson, St. Louis, 1915 ; and "Innere Sekretion," by A. 

 Biedl, Wien, 1916. The last three contain bibliographies, very complete 

 up to the dates of their respective publications. 



