THE THYROID AND PARATHYROIDS 321 



operations (first those of one side, then those of the opposite 

 side) showed that the first operation produced little or no 

 result ; the second operation proved rapidly fatal. Dogs could 

 be kept in good health with only one parathyroid remaining, 

 but the authors suspected that chronic symptoms might arise 

 at a later period. 



In a still later communication the Italian authors state that 

 the tetany induced by thyroidectomy is less marked in old dogs 

 than in young ones. The tetany is particularly well-marked 

 in dogs, if, after removal of the thyroids, they are fed abun- 

 dantly on a meat diet. If the animals are allowed to get into a 

 condition of hunger, the tetany becomes much less noticeable. 



Results similar to those of Vassale and Generali have been 

 obtained by several observers. 



The present writer, working in conjunction with Professor 

 W. A. Jolly, encountered difficulties where, from previous study 

 of the literature, they had not been led to expect them, and 

 could by no means always induce death in animals by total 

 parathy roidect omy . 



From the writings of most authors it would appear to be a 

 simple matter to remove, in some cases, the parathyroids 

 leaving the thyroid intact, and in others the thyroid leaving 

 the parathyroids in situ. Variations of these experiments 

 would appear to be equally simple. Welsh, indeed, who 

 worked with the cat, in which parathyroidectomy presents, 

 perhaps, least difficulty, admits some difficulties in performing 

 complete parathyroidectomy. According to Vincent and Jolly, 

 Welsh has understated these. The obstacles in the way of 

 success in this operation are mainly anatomical. The para- 

 thyroids are extremely variable in position. The external pair 

 may, as a rule, be easily seen and removed, but the internal are, 

 in the majority of cases, embedded deeply in the substance of 

 the thyroid. When it is remembered how vascular thyroid 

 tissue is, how slightly the parathyroid differs from it in appear- 

 ance to the naked eye, and how this difference, slightr as it is, 

 entirely disappears when there is any bleeding, it will be seen 

 that the operation of digging out the internal parathyroid is 

 one of extreme delicacy. A further difficulty presents itself in 

 the fact that there is a nodule of thymus also embedded in the 

 thyroid lobe, frequently in close proximity to the internal 

 parathyroid, resembling it on naked-eye examination, and 



21 



