PARATHYROID GLANDS 597 



one suspect tetany at all, it is well to keep the pressure applied for at least 

 five minutes before admitting that the Trousseau phenomenon cannot be 

 made manifest. Clinicians were earlier exercised to decide whether 

 the pressure that elicits the Trousseau phenomenon acts through mechan- 

 ically stimulating the nerves or through cutting off the blood supply. Von 

 Frankl-Hochwart's experiment bearing upon this point seems to me con- 

 clusive. He found in experimental tetany in the dog that the slightest 

 pressure applied to the exposed nerve sufficed to set free the contracture, 

 whereas the strongest pressure upon blood vessels alone remained without 

 effect. 



The gradual appearance of the contracture when the Trousseau 

 phenomenon is elicited is another point that I should like to emphasize. 

 One sees the fingers begin to straighten out and to become adducted, and 

 the thumb is gradually opposed and adducted and slowly turned into the 

 palm. The Trousseau phenomenon, as it develops, is a most interesting 

 clinical sign to watch. 



A pseudo Trousseau phenomenon has been described as occurring in 

 hysteria. But if one be familiar with the true Trousseau phenomenon 

 and its gradual appearance, he will rarely be deceived by the simulation 

 of a hysterical. I should advise caution, too, before assuming that a con- 

 tracture resembling a Trousseau phenomenon is due to hysteria rather 

 than to tetany, even in a patient known to be hysterical, for hysteria and 

 tetany may occur together in the same person. 



Though tetany may exist in persons in whom the Trousseau phenom- 

 enon cannot be elicited, nevertheless it is positive in so large a proportion 

 of cases that it is a sign exceedingly valuable to the diagnostician. Von 

 Frankl-Hochwart has estimated that the Trousseau phenomenon is posi- 

 tive in two thirds or three fourths of all cases of tetany, manifest and 

 latent. 



Though all are now agreed that the pressure applied to call forth the 

 Trousseau phenomenon is effective through stimulating the nerve rather 

 than through cutting off the blood supply, it is still undecided whether 

 the Trousseau, phenomenon is a response due to direct stimulation of the 

 hyporexcitable motor nerves, or whether it is a reflex phenomenon, that 

 is, one in which the motor response is produced indirectly by stimulation 

 of the sensory nerves. Schlesinger, a careful Viennese observer, has 

 strongly championed the latter view. He argues that the Trousseau 

 phenomenon can scarcely be due directly to mechanical stimulation of 

 the hyperexcitable motor nerves, since response to mechanical excitation 

 is most marked in the facial nerve, and compression of that nerve in the 

 face does not lead to tonic spasm. Furthermore, the Trousseau phenom- 

 enon is most marked in the arms, where the nerves are only moderately 

 mechanically excitable, and even when mechanical hyperexcitability in a 

 given person is very distinct in the arm nerves it may not be possible 



