512 SUTHERLAND SIMPSON 



sions. It was the generally accepted belief, at this period, that the deter- 

 mining facto; 1 was metabolic. 



Observations After the Discovery of the Parathyroids as Indepen- 

 dent Entities. The external parathyroids were discovered by Ivar Sand- 

 strom in 1880. He found these bodies constant in fifty autopsies in man, 

 and he also studied and accurately described their position and structure in 

 the dog, cat, rabbit, ox, and horse; nevertheless, his work was lost sight of, 

 and in extirpation experiments on the thyroid no cognizance was taken of 

 these bodies. It was not until their rediscovery by Gley (a) in 1891 that 

 they received the attention of physiologists. 



' The work of Gley may be said to mark the beginning of the second 

 epoch in the history of the physiology of the parathyroid glands. Prior to 

 this, the effects which we now believe to be due to absence of parathyroid 

 tissue were ascribed to thyroid deficiency. In 1892 Gley (&) published 

 several papers describing the results of his experimental work on the para- 

 thyroids. In the rabbit he found two glands, one on each side, some dis- 

 tance below the lower pole of the lateral lobe of the thyroid. Their location 

 was such that previous workers, unaware of their existence, in removing the 

 thyroid, had, in all probability, left them untouched. In the dog, on the 

 contrary, the glandules were found closely applied to the external surface 

 of the lateral lobe of the thyroid and within its capsule, so that here they 

 must always have been removed along with the thyroid lobes. As Gley 

 understood it at that time, two quite different operations had been per- 

 formed by his predecessors in this field ; in the one case (rabbit) simple 

 thyroidectomy, in the other (dog) thyroparathyroidectomy. 



Difference Between Thyroid and Parathyroid Manifestations. In his 

 first series of experiments Gley removed both the thyroids and parathy- 

 roids from sixteen rabbits. Fourteen of these were seized with acute 

 symptoms, which began one day after the operation and proved fatal with- 

 in a few hours. In the light of subsequent experiments on this animal, 

 this seems to be an unusually large proportion. When he removed the 

 parathyroids and left the thyroids untouched, and, vice versa, when the 

 thyroid lobes were taken away and the parathyroids left behind, no acute 

 symptoms followed. He also showed that in the dog, when he removed 

 the thyroid, taking C are to leave behind the two parathyroids, the animal 

 showed no immediate ill effects. At the time of his earlier experiments 

 Gley was not aware of the existence of the internal parathyroids; these 

 were described, for the first time, by Kohn (a) in 1895. 



The explanation offered by Gley for the difference which all previous 

 workers had found in the effects following so-called thyroidectomy in the 

 carnivora and horbivora, respectively, were based, not on the character of 

 the metabolic processes of the animal, but on purely anatomical grounds. 

 In the carnivora the operation was complete, all the thyroid tissue having 

 hcen removed; in the herhivora, on the other hand, some, in the form of 



