760 THE ENDOCRINE ORGANS, OR DUCTLESS GLANDS 



"When the tetany is the result of a complete extirpation of all parathy- 

 roid tissue, the symptoms can be combated by a successful transplan- 

 tation or graft of parathyroid tissue made from an animal of the same 

 species. Indeed, it has been found that the success of a graft of parathy- 

 roid is assured only when the graft is derived from the same kind of 

 animal as that from which the parathyroid has been removed. Implan- 

 tation into the subcutaneous tissue of a tetany patient of parathyroid 

 tissue obtained fresh from the deadhouse has been performed with bene- 

 ficial outcome. 



Noel Paton, Findlay and Watson 80 have recently contributed greatly 

 to our knowledge of the physiological pathology of tetania thyreopriva, 

 as the above condition is called. The symptoms are not due to any con- 

 dition affecting the muscles themselves, since they disappear after sec- 

 tion of the nerves. Nor are they primarily dependent upon the cere- 

 brum or cerebellum, since ablation of neither abolishes them. This does 

 not imply that secondary involvement of the higher centers never oc- 

 curs; on the contrary, the epileptiform convulsions and disturbances of 

 equilibrium sometimes observed indicate cerebral or cerebellar involve- 

 ment, respectively. This leaves some part of the lower neuron reflex 

 arcs as the site of involvement, It is not the afferent neuron, since the 

 tremors and jerkings persist after section of the posterior roots, leaving 

 the efferent neuron as the affected structure. 



The foregoing conclusion led Paton and his co-workers to compare the 

 response of muscle and nerve to electric, stimulation in normal and 

 parathyroidectomized animals. Although there are considerable varia- 

 tions in the responses of a normal animal, they are very definitely ex- 

 aggerated in tetany when either the motor neuron or the muscle itself 

 is stimulated, the exaggeration in the latter case being dependent upon 

 alterations in the neural structures (nerve endings) in the muscle. The 

 increased electric excitability can not, however, be taken as a measure 

 of the severity of the condition, for it may be no more marked in cases 

 in which there is involvement of the cerebral hemisphere (causing epilep- 

 tiform fits) than in milder cases. 



As to the cause of the symptoms, many possibilities have to be con- 

 sidered. In the first place, no direct relationship exists between the 

 thyroid and parathyroid in this connection. One cause might be the 

 absence of some substance which normally checks the activity of the nerv- 

 ous system, some chalone in Schafer's sense. That such is not the case is 

 shown among other tilings by the fact that bleeding and then transfusing 

 normal saline immediately removes the symptoms for some time. Moreover, 

 the metabolic disturbances go on when the nervous symptoms are slight. 

 It had previously been thought by W. <■'. Macallum 83 that, since symp- 



