THE PAEATHYEOID GLANDS 521 



badger is totally unaffected by the complete removal of the thyroid and 

 parathyroid glands. 



Their final conclusion is, in part, as follows: "Neither thyroids nor 

 parathyroids can be considered as organs absolutely essential to life. 

 When parathyroidectomy proves fatal, this is probably due to the severe 

 damage done to the thyroid, and it is possible that there may be a differ- 

 ence between the results of severe damage to the thyroid apparatus and its 

 total removal. Thyroids and parathyroids are to be looked upon as a 

 single physiological apparatus, the two kinds of tissues being intimately 

 associated embryologically and working together physiologically. When 

 the thyroid is removed, the parathyroids appear capable of functionally re- 

 placing it to a certain extent, and their histological structure changes 

 accordingly." This seems to be essentially the original view of Gley, 

 which he abandoned later. 



Forsyth (&) (1908) appears to support the conclusions of Vincent and 

 Jolly. In a. review of the recent work on the subject, up to 1908, he sums 

 up as follows: "Kestricting our attention to these observations on the 

 parathyroids which have led to fatal results, we find, in the first place, that 

 only a percentage (varying from about 15 per cent to about 90 per cent) 

 of the animals experimented upon die, or even develop symptoms, within 

 a reasonable period. These figures are inclusive of every pathological de- 

 velopment subsequent to the operation, yet a certain number of these results 

 must be surely coincidental." He expresses the opinion that the para- 

 thyroids are glands essentially thyroidal in nature, possessing no peculiar 

 function, but engaged in the active secretion of the same substance as the 

 thyroid ; they are, in fact, portions of the main thyroid gland which have 

 assumed functional activity but have not yet formed vesicles ; if, however, 

 the thyroid be removed, they may develop into thyroidal tissue. 



The conclusions of Vincent and Jolly and of Forsyth are contrary to 

 the generally accepted doctrine, and few subsequent workers have sup- 

 ported them. Vincent has more recently (1920) expressed doubt as to the 

 validity of his former view. 



In 1911 Halpenny and Gunn working in Vincent's laboratory in 

 Winnipeg, repeated the experiments of Vincent and Jolly on monkeys, and 

 the effects of the operation have been much more serious in their hands, 

 All their animals, eight in number, with one exception, began to show 

 symptoms very early one on the third day after the operation, three on 

 the fourth day, two on the fifth day, and one on the thirteenth and in 

 every case there was a fatal termination. One animal remained well until 

 the .seventy-first day, but died ten days later. 



The opponents of Vincent and Jolly, of Forsyth, and of others who 

 support them, explain the comparatively large number of cases that show 

 no symptoms after removal or destruction of all four parathyroids in the 

 hands of some experimenters as due to the presence of accessory parathy- 



