526 SUTHERLAND SIMPSON 



how preconceived ideas may influence the logic of experienced scientific 

 investigators. 



Kossi (f911) in sheep and goats finds, like the last observers, that 

 total parathyroidectomy is often very well tolerated in these animals, while 

 in some cases it leads to tetany, convulsions, and death. He does not give 

 the body weights, and draws no distinction between adults and young ani- 

 mals regarding the severity of the effects. He also believes that failure to 

 produce acute symptoms is due to the presence of accessory parathyroid 

 tissue unintentionally left behind at the operation, although he did not 

 find any such on the most careful postmortem examination. 



Berkeley and Beebe (a) state that in dogs, after total parathyroid ex- 

 tirpation, the symptoms are more severe in young than in old animals. 



Marine, as the result of his own observations, believes that the young 

 are more susceptible than the old. He ligated the superior thyroid arteries 

 in four puppies of the same age (sixty-two days) and litter, and in all 

 tetany developed on the following day, eighteen hours after the ligations. 

 All died a few days later. The inferior thyroid artery, which is normally 

 very small in the dog, was intact and uninjured. In twelve similar opera- 

 tions in adult dogs, none developed tetany. This was, of course, not 

 equivalent to complete thyroparathyroidectomy, but the operation was 

 identical in the two cases. 



Simpson found that in sheep age has a profound influence. Four 

 lambs, after the complete operation, showed acute tetany, which ended 

 fatally, while in adult sheep the same treatment led to no visible effects 

 within the three or four months they were kept alive. 



Effects of Diet, Pregnancy and Other Factors on Parathyroid Tetany. 

 Paton and Findlay (b) discuss certain factors which may modify the 

 rapidity of onset and the character of the symptoms, viz., diet, age, rickets, 

 pregnancy, and lactation. They confirm, in their own experiments, a state- 

 ment made by many previous observers, viz., that feeding with meat has a 

 marked effect in increasing the severity of the symptoms, and they fre- 

 quently employed this method to induce the onset when the condition was 

 latent. They failed to observe any evidence on the effect of age in the dog, 

 but they noted that in very young animals the tonic were more pronounced 

 than the clonic muscular contractions. 



They found that rickets appeared to have some influence. They did 

 the complete operation on five puppies about seventy days old with active 

 rickets ; in three of them symptoms appeared within twelve hours and in the 

 other two within twenty-four. In puppies of about six months, with healed 

 rickets, the symptoms did not supervene any sooner and were no more 

 acute than in non-racliitic dogs'. It would, therefore, appear that active 

 rickets does have an accelerating and accentuating effect on the conditions 

 la-ought about by parathyroidectomy. In this Paton and Findlay support 

 the previous work of Marine and others. 



