520 SUTHERLAND SIMPSON 



close proximity to the internal parathyroid, resembling it on the naked eye 

 examination, and therefore easily mistaken for it in the course of the 

 operation/' Bearing all these difficulties in mind, these observers do not 

 hesitate to declare that, except in very favorable cases, in which the inter- 

 nal parathyroid chances to lie near the surface of the thyroid lobe, the 

 operation is an impossible one. The injury caused to the thyroid by 

 attempts to enucleate the internal parathyroids, they believe, may be held 

 to account for the deaths of many animals in the hands of other experi- 

 menters, which at the time were attributed to parathyroid insufficiency. To 

 remove all thyroid tissue, leaving the parathyroids, particularly the inter- 

 f nal pair, with their blood supply undamaged, they regard as still more 

 difficult. 



In their experiments on cats, when one thyroid lobe was left and one 

 parathyroid, or two thyroid lobes with one parathyroid, the animals re- 

 mained perfectly well. When parathyroids alone were left, out of five 

 cases, one proved fatal. When the thyroid was left and all four parathy- 

 roids successfully removed, only 33 per cent proved fatal. One of these 

 did not show typical symptoms, and in the other two fatal cases, the thy- 

 roid gland was found at the postmortem examination to be extensively 

 damaged. "In the great majority of cases no ill effects of any kind re- 

 sulted from the operation." Simple parathyroidectomy in the cat, when 

 the thyroid is left unimpaired, is not necessarily fatal. Their fatal cases 

 were those in which they had clone most damage to the thyroid. This was 

 directly opposed to the prevailing view. 



Out of five dogs, the complete operation in one produced no symptoms, 

 and in this case no accessory parathyroids were found later when the 

 animal was killed. 



In foxes symptoms appeared within five hours in two cases, and prob- 

 ably in a third, and death soon supervened. Foxes were the most purely 

 carnivorous animals employed. 



In monkeys removal of the parathyroids together with the thyroids did 

 not prove fatal, although in some cases transient nervous symptoms were 

 observed. In these animals, according to Vincent and Jolly, neither the 

 thyroids nor the parathyroids are essential to life. 



In the rat thyroid and parathyroids may be destroyed without affect- 

 ing the animal in any way. In guinea pigs similar results were obtained, 

 but in rabbits the matter was doubtful. 



As determining the result, they seem to attach great importance to the 

 metabolic habits of the species. The variable effects produced in different 

 animals cannot be explained on anatomical grounds, nor are they probably 

 due to mere variations in feeding, but rather to deep seated physiological 

 conditions. 



.In their second paper (1905) they confirm their former findings and, 

 in addition, make the statement that such a carnivorous animal as the 



