PAEATHYROID GLANDS 599 



highest grade of mechanical excitability is somewhat rare. It is much 

 more common to meet with the second grade (Chvostek //), in which 

 movement of the nostrils (M. nasalis), and a drawing of the angle of 

 the mouth to the side (M. quadratus labii super ioris) follow tapping 

 upon a spot beneath the zygoma. The third grade of positive reaction 

 (Chvostek III), indicating a still lower degree of mechanical excitability 

 of the facial nerve, is manifested as a slight twitch at the angle of the 

 mouth when the same region is -tapped. 



This facial phenomenon, or Chvostek's sign, is certainly very valuable 

 for quickly yielding a clew to the possible existence of tetany, since it can 

 be performed on a suspect in a moment or two. It is, however, sometimes 

 absent in true tetany, and it may be positive in cases in which there is no 

 other reason for assuming the existence of tetany (psychoneurotic states, 

 tuberculosis, Graves' disease, etc.). It appears to be more constantly 

 present in the tetany of adults than in that of children (Schlesinger), and 

 to be more frequently met with in chronic than in acute tetany (von 

 Frankl-Hochwart). According to Weiss, it may sometimes be positive in 

 normal persons. During epidemics of tetany in Vienna, von Frankl- 

 Hochwart could often demonstrate the presence of Chvostek's sign in 

 apparently healthy people, but admitted that this might mean the exist- 

 ence in such persons of formes frustes of tetany. 



It seems certain that Chvostek's sign depends upon a direct mechanical 

 hyperexcitability of the facial nerve, and not upon an abnormal reflex 

 activity. The arguments pro and con have been marshaled by von Frankl- 

 Hochwart. 



In sucklings, one can sometimes elicit, instead of a typical Chvostek 

 sign, a lightning-like contraction in the orbicularis oris muscle simply 

 by gently tapping the lips of the infant with a percussion hammer. 



Another sign that is doubtless due to mechanical hyperexcitability of 

 the motor nerves is F. Schultze's (b) tongue dimple sign. The patient is 

 asked to protrude the tongue, and the observer taps it lightly with the per- 

 cussion hammer. At the site of application of the mechanical stimulus, a 

 depression or dimple appears. The same sign is sometimes met with also 

 in myotonia congenita (Thomson's disease). 



Increased idiomuscular excitability is sometimes demonstrable in 

 tetany. One tests for it by tapping the surface of a muscle, say the 

 pectoralis major, with a percussion hammer, and compares the response 

 elicited with that obtainable in normal persons. 



The Arm and Leg Phenomena of Tetany 



In 1906 E. H. Pool (a) of New York, studying a case of postoperative 

 tetany through a long period at the French Hospital, observed the con- 

 stant response of contracture of the muscles of the upper extremity upon 



