PAKATHYKOID GLANDS 667 



They represent mere gropings toward the satisfactory explanation that 

 subsequent research will render possible. 



11. The Site and Mode of Action of the 

 Tetany Poison 



An examination of the symptoms and signs of tetany has shown us very 

 clearly that, both in man and in experimental animals, the nervous system 

 is profoundly affected, chiefly in the direction of increased excitability of 

 the motor, sensory and visceral nerves to mechanical, chemical and elec- 

 trical stimuli. 



All the principal signs of tetany carpopedal spasms, Erb's phenome- 

 non, Trousseau's sign, Chvostek's phenomenon, Hoffmann's phenomenon, 

 increased epinephrin sensitiveness, increased pilocarpin sensitiveness, epi- 

 leptiform attacks point to increased excitability. Signs of depression of 

 excitability, at least in certain domains, are, however, also met with, includ- 

 ing diminution of the deep reflexes, flaccid pareses, diminution in the 

 efficiency of the gastric and intestinal motor mechanisms (Carlson), and 

 increased heat loss due to depression or to paralysis of the vasoconstrictor 

 mechanism of the blood vessels (Smith). 



In view of the obvious alterations in the nervous functions in tetany, 

 many attempts have been made to determine the exact localization of the 

 action of the poison in the nervous tissues. The papers of 0. Lanz (1894), 

 W. G. MacCallum (1909), Carlson and Jacobson, F. T. Shepherd and 

 Wesley Mills, Falta and Kiidinger (1909), H. J. Mustard (1911-12), and 

 A. Biedl (1913) bear upon this phase of the subject. 



In summary, it may be -said that the observations thus far made, 

 though they permit us to state that there is a heightened excitability of the 

 nerve centers and of the peripheral nerves, and that certain central (prob- 

 ably subcortical) neurons are affected, do not adequately reveal the exact 

 anatomical and histological localization of the specific effects of the tetany 

 poison. It is conceivable that some of the mechanisms that participate in 

 the production of the remarkable tonic contractures that characterize the 

 so-called decerebrate rigidity of experimental animals may be specifically 

 acted upon by the tetany poison. Certain it is that the effect is exerted 

 upon the neural mechanisms themselves and not directly upon the muscles 

 innervated by the motor nerves. Furthermore, the change produced in the 

 nervous system is not inflammatory in character, nor can it be merely a 

 circulatory disturbance ; it is probably of a toxic degenerative nature. 



