

PAEATHYROID GLANDS 605 



contraction approach one another much more closely in tetany than under 

 normal conditions. 



5. The observation of kathodal closure tetanus (KCTe) yields only 

 a very unreliable clew for increased excitability of the motor nerves. 



6. Tests made with the faradic current also reveal in tetany, on the 

 average, an outspokenly increased excitability of the motor nerves, but 

 these faradic tests are not sufficiently characteristic in all cases for the 

 recognition of increased excitability. 



7. An increase of the electrical excitability of the motor nerves is 

 demonstrable in all cases of tetany, if the above criteria be observed ; and 

 there are good grounds for the belief that cases occur in which such in- 

 creased excitability is the sole symptom of the disease. 



The value of testing the galvanic excitability of the motor nerves for 

 the diagnosis of tetany in children can scarcely be overemphasized. The 

 studies of Escherich, Ganghofner, and others early demonstrated the in- 

 crease of electrical excitability of the motor nerves in tetany in suck- 

 lings, and, ever since, this increased excitability has been generally recog- 

 nized as an essential mark of the syndrome. 



Following upon the important studies of Mann and of Thiemich, 

 summarized above, C. von Pirquet (a), in 1907, made careful studies of 

 electrical excitability in normal children and compared the values obtained 

 in them with those that are observable in children that suffer from tetany. 

 Von Pirquet followed a precise technique in testing for increased galvanic 

 excitability of the motor nerves in infants and young children. The child 

 is laid upon its back, the large indifferent electrode upon the abdomen; 

 the small electrode (Stintzing's normal electrode with interrupter) is 

 placed upon the point to be stimulated. 



Von Pirquet prefers to stimulate the nervus peroneus, since contrac- 

 tions in the nervus medianus are less satisfactorily demonstrable, on ac- 

 count of the finger movements that go on continuously in infants, and 

 because tests on the facial nerve require currents strong enough to be 

 painful. Moreover, the nervus peroneus has the advantage that it can be 

 reached without removal of the child's shirt. 



The child's left knee is seized by the left hand of the examiner, who, 

 with his right hand, presses the stimulating electrode into the lateral part 

 of the popliteal! space. The electrode has a firmer seat there than upon 

 the other motor point of the nervus peroneus on the lateral surface of the 

 fibula. The mother holds the indifferent electrode upon the abdomen 

 of the child with her left hand and with her right hand gradually alters 

 the strength of the current of the galvanic apparatus as directed by the 

 examiner. It is more convenient, of course, if, for the latter manipula- 

 tion, one has an assistant at hand, but the procedure can be carried out 

 with the aid of the mother alone. 



At the beginning of the test the stimulating electrode is used as 



