!' ATHOGENESIS OF TETANY 2OI 



as established that experimental tetany depends on the loss or marked 

 damaging of the parathyroid glands. This holds good for all species of 

 animals. The course of tetany in different animals is, however, different. 

 In some after total extirpation of all the parathyroids there occurs an acute 

 tetany, which after a short time leads to death. In others, for instance in 

 monkeys, the course is chronic. Does the complete loss of parathyroid 

 glands lead to tetany always? 



Here should be mentioned that all authors are agreed that older animals 

 resist the operative attack more readily than young ones. Important in 

 this respect are the investigations of Iselin, who found that the young of 

 partially parathyroidectomized rats are especially sensitive to the extirpa- 

 tion of the parathyroids, and die in a few hours with fulminating epilepti- 

 form seizures. Moreover, there are numerous statements that the simul- 

 taneous extirpation of thyroid gland and parathyroids is better borne than 

 isolated parathyroidectomy. Many hypotheses have been advanced to 

 explain this fact, a fact that our own investigations fully substantiate. The 

 most natural of these seems to me to be the conception that on the simul- 

 taneous extirpation of the thyroid glands the metabolism and with it the ex- 

 citability of the entire nervous system is reduced, and the function of the 

 parathyroid glands is then reduced in its action. On the other hand, we 

 know that procedures of the most diverse kinds and conditions that make 

 great demands on the nervous system accelerate the outbreak of tetany or 

 allow latent forms to pass over into the acute forms. If we here recog- 

 nize too that the influences that may modify the course and acuity of the 

 process may be manifold, we may well assume that the complete loss of all 

 parathyroids leads to death in all species of animals, under the manifesta- 

 tions of an acute or more chronic tetany, hence that the loss of the para- 

 thyroid function is incompatible with the long continuation of life. I would 

 not off-hand relinquish this assumption on account of the quite isolated 

 contrary statements. Haberfeld and Schilder state that rabbits in which at 

 first the four parathyroids are removed, and later the thymus gland with 

 the accessory thyroid, continue to live. Continuous serial sections show 

 the absence of any parathyroid tissue. Wiener even asserts that of forty-five 

 parathyroidectomized animals, 20 per cent, did not show any manifestations 

 of tetany. In my own numerous experiments on dogs, cats and rabbits, I 

 have never seen an animal survive. The unconditional importance of the 

 function of parathyroids for life is also held by Biedl, Hagenbach, and 

 others. As long, therefore, as no further statements as to this question 

 exist, I would still believe that in the experiments of Haberfeld and Schilder 

 and Wiener that have been mentioned, accessory thyroids may have escaped 

 demonstration. 



As regards the mechanism of parathyroid function, numerous opin- 

 ions have been promulgated. In the foreground stands the views as to 



