THE THYROID APPARATUS 59 



The results obtained by Parhon and Urechie, Berkeley and 

 Beebe, and Bell and Martin, Ott, and by my own researches, 

 furnish unquestionable proof of the susceptibility of tetany to the 

 therapeutic influence of calcium salts. Slight, and even more 

 severe, attacks are very much ameliorated by the exhibition of 

 these salts, the symptoms sometimes disappearing altogether. 

 After eighteen to twenty-four hours, the symptoms return in 

 their former intensity. I did not find that the daily administra- 

 tion of calcium salts had any effect in prolonging the life of cats 

 from which the thyroid and parathyroids had been removed. It 

 must, however, be borne in mind that our knowledge of the 

 therapeutic effects of calcium salts in tetania parathyropriva does 

 not justify us in forming a definite conclusion with regard to the 

 pathogenetic significance of these salts. It appears very probable 

 that the calcium salts exercise an inhibitory effect upon the patho- 

 logical muscular convulsions, similar to that which they exercise 

 upon all forms of muscular contraction. This applies to the other 

 kathions (magnesium, barium, strontium), which also exercise a 

 favourable influence upon tetanic convulsions. 



THE POINT OF ATTACK OF THE HYPOTHETICAL 



TETANY TOXIN. 



The first experiments with the object of localizing the seat 

 of tetany were carried out by O. Lanz in Horsley's laboratory. 

 Similar investigations have recently been undertaken by Mac- 

 Callum, by Falta and Rudinger, and by Biedl. The results are 

 as follows : 



If, after parathyroidectomy, the nerve of one of the extremi- 

 ties is severed, no convulsion will take place in that limb. If 

 the nerve is resected at a moment when the whole body is con- 

 vulsed with tetany, the muscular contractions of that limb will 

 cease, and the hypersensibility of the nerve will rapidly disappear. 

 Pressure upon a nerve which has been severed some hours pre- 

 viously, will not produce a muscular contraction ; also, the nerve 

 is insensitive to galvanic stimulus. I have confirmed these 

 results by repeated experiment, but the findings do not agree with 

 those obtained by Falta and Rudinger. These observers severed 

 the sciatic nerve after the appearance of tetany; they found that 

 the electric hypersensibility persisted for several days and that the 

 normal irritability of the nerve persisted until the death of the 

 animal, which occurred nine days later. This discrepancy in 

 the findings is probably explained by the fact that in each case 

 I severed the whole of the nerve plexus of the front extremity, 

 while Falta and Rudinger severed the sciatic nerve only. The 

 resection of the sciatic nerve alone is not sufficient to arrest the 

 muscular contractions in the limb, and MacCailum for this reason 



