624 LEWELLYS F. BAKKER 



produced in young rats by parathyroidectomy followed by transplantation 

 of parathyroid tissue into the spleen, have been made by Iselin. The 

 animals were retarded in their growth and rontgenological examinations 

 of their skeletons revealed a diminution in the size df their bones, though 

 their normal forms were preserved. The histological changes in these 

 bones resembled more closely those of rickets than those of athyreosis. 



Fractures of bones heal less well in hypoparathyroidism than in normal 

 animals (Canal, Morel), owing to delayed ossification of the callus, a 

 defect that can apparently be overcome by the administration of para- 

 thyroid gland substance. 



14. The Endocrine Glands in Tetany 



Parathyroid Glands 



That the symptoms of tetany are identical with those that follow 

 removal of all, or of a part, of the parathyroid glands, has been definitely 

 proven both for animals and man. Every one now agrees that tetania 

 strumipriva is, in reality, a tetania parathyropriva, and the majority 

 of clinicians and experimental physiologists believe that, in several, if 

 not in all, the other forms of tetany, we have also to deal with parathyroid 

 insufficiency. The relation of the parathyroid glands to tetany is so fully 

 discussed in other sections of this article (see Historical Notes and Etiology 

 and Pathogenesis) that further comment here is unnecessary. 



Thyroid Gland 



Some investigators hold that the thyroid and the parathyroids are 

 organs that can reciprocally, in case of need, act, to a certain extent, 

 vicariously one for the other; others maintain tha!; no such reciprocal 

 vicariousness of function is possible, and that the thyroid and the para- 

 thyroids are functionally antagonistic organs. The evidence thus far 

 available scarcely suffices for the complete substantiation of either view, 

 and more work must be done before the matter can be considered to be 

 settled. 



Those who support the doctrine of reciprocal antagonism can adduce 

 many observations that they think favor it. Thus, the tetany that follows 

 simultaneous extirpation of the thyroid gland and the parathyroid glands 

 seems to be of a milder type than that which follows parathyroidectomy 

 alone. It has been suggested that this relative mildness is due to a lack 

 of the reinforcement by the thyroid of the parathyroid insufficiency pro- 

 duced by extirpation of the parathyroid glands; if the thyroid were not 

 removed the parathyroid defect would be more strongly in evidence. 



