i INTEKNAL PEOTECTIVE SECKETIONS 33 



proportion as the thyro-parathyroid excision was more complete. 

 Sometimes the animals succumbed after incomplete ablation of 

 the parathyroid glands, i.e. when one parathyroid only was left 

 in situ, as usually occurs in the case of dogs that have more than 

 four parathyroids. As a rule, however, the animals that survive 

 partial thyroidectomy exhibit slight and transitory pathological 

 symptoms. These are analogous to the effects of thyro-parathy- 

 roidectomy acute phenomena of " tetania thyreopriva," which is 

 speedily fatal, or slight and transient, according as the para- 

 thyroidectomy was complete or partial. When partial para- 

 thyroidectomy is associated with total thyroidectomy, the chronic 

 phenomena of cachexia thyreopriva set in, with or without slight 

 convulsions. 



In view of their significance, the experiments of Vassale and 

 General! were at once repeated and confirmed in France by 

 Moussu (1897). Of four dogs on which he performed total 

 thyroidectomy, three died of tetany on the 2nd and 7th day, 

 and the fourth survived because (as shown at the post mortem) it 

 had a fifth supernumerary parathyroid. 



Edmunds and Welsh (1898) independently repeated and con- 

 firmed the results of Vassale in England. 



The same work was continued in Italy by Capobianco and 

 Mazziotti (1899), and more extensively by Lusena (1899). The 

 latter, in a fine series of comparative experiments on dogs, 

 shows 



(a) That the (chief) characteristic symptom of thyro-para- 

 thyroidectomy is coma, the period from the operation till death 

 being on an average 10 days ; 



(5) That the characteristic symptom of parathyroidectomy is- 

 tetany, the interval between the operation and death being usually 

 3 days ; 



(c) That the excision of the thyroid, including the two internal 

 parathyroids (which, as we shall see, are included with them) is 

 not fatal if perfect nutrition is maintained in the two external 

 parathyroids which are left in situ. 



Lusena, in order to confirm the fact that the presence of 

 the thyroids aggravates the pathological syndrome of total 

 parathyroidectomy, conceived the idea of excising the thyroids 

 in dogs already deprived of their parathyroids, which were on 

 the ppint of dying from tetany, and saw that the convulsive 

 phenomena were gradually attenuated, and a state of comparative 

 amelioration introduced, so that the fatal issue was postponed. 



The effects of parathyroidectomy can also be attenuated by 

 the so-called substitutive therapeutics, i.e. by hypodermic, or better 

 intravenous, injections of aqueous extract of the parathyroids 

 alone. These experiments were performed almost simultaneously 

 by Moussu and by Lusena (1898). Moussu showed that such 



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