Effects of Removal of Parathyroids 23 



or chronic : in the former clonic, in the latter tonic contractions of the 

 muscles tend to manifest themselves. 



Tetany is without doubt due to deprivation of the parathyroids, for 

 it will occur when these alone are removed. It varies greatly in severity 

 and often takes on an intermittent character. The symptoms may 

 remain latent for a considerable time, and only show themselves as the 

 result of some unusual condition such as pregnancy. The effect is on 

 the lower neurones, for according to Horsley it is not arrested by abla- 

 tion of cerebral cortex. Lanz and Biedl state that it is increased on 

 the side of the ablation; with cerebellar lesion they find an increase 

 on the opposite side. According to Mustead, section of dorsal roots does 

 not affect it. After spinal transection it disappears below the level of 

 the lesion. Tetany is relieved by injection of parathyroid extract, and in 

 many cases by administration of thyroid substance : it is uncertain if 

 this last result is due to included parathyroid. When tetany is produced 

 by total extirpation of all parathyroid tissues it can apparently only 

 be cured by a successful graft of a parathyroid from an animal of the 

 same species. The condition has been found to occur after complete 

 removal of the thyro-parathyroid apparatus in man, and may be suffi- 

 ciently serious to threaten life, unless suitable measures are taken to combat 

 the effects of parathyroid loss. 1 



In order to prevent the accession of tetany in operations for removal 

 of thyroid tumours it is usually necessary to leave at least two of the 

 four parathyroids. In one dog experimented on by Edmunds, he found 

 that a single parathyroid was sufficient to prevent the onset of tetany 

 (the three others and both lobes of the thyroid having been removed) : on 

 extirpation of the remaining parathyroid the animal speedily developed 

 tetany. 



Animals with insufficient amount of parathyroid tissue may not suffer 

 from tetany under ordinary circumstances, but the symptoms may come on 

 under special conditions. Thus Vassale observed, in a bitch from which 

 three of the four parathyroids had been removed, that the animal was 

 especially subject to fits of tetany during pregnancy 2 and lactation. The 

 character of the food also influences the onset of the symptoms, flesh 

 foods being much more apt to bring on the condition than a vegetable or 

 milk diet. 



1 A case in which all possible remedies, and grafts from various animals, including a 

 monkey, were tried without avail, but which was rapidly and completely cured by the 

 implantation into the subcutaneous tissue of parathyroids obtained fresh from the dead- 

 house, is described by W. H. Brown in the Annals of Surgery, vol. liii., 1911. In ex- 

 periments on animals it has been almost universally found that to ensure the success of a 

 graft of parathyroid it must be derived from the same animal from which the parathyroids 

 have been removed (Halsted and others). 



2 This is contrary to what might be expected, considering that the mother would have 

 had the parathyroids of the foetuses to draw upon. It seems, however, to be confirmed by 

 the results of other experiments on dogs, and also by those of Acller and Thaler upon 

 partially parathyroidectomised rats. Animals which have suffered complete parathyroidec- 

 tomy do not become pregnant. 



