GRAVES' DISEASE 83 



the section of the motor nerves, they must be 

 central in origin ; and it is probable that they 

 result from abnormal excitability of the spinal 

 motor neurons. The condition is known as 

 tetany, and although recovery frequently occurs, 

 it is sometimes fatal in a few days, more especially 

 in carnivora and in young animals. There is 

 some evidence that vaso-motor reflexes are evoked 

 more readily after parathyroidectomy, and that 

 the irritability of the sympathetic system is also 

 exaggerated. Noel Paton has shown that the 

 injection of guanidin is followed by symptoms 

 which closely resemble those of parathyroid 

 tetany, and he has brought forward some evidence 

 which suggests that the function of these glands 

 is to control the metabolism of guanidin and that 

 this substance accumulates in the blood when the 

 glands are removed." Of this substance, one of 

 the derivatives of purin, Bainbridge again says : 

 " After its absorption the nucleic acid taken as 

 nucleo-protein in the food is broken down by a 

 series of enzymes, called nucleases, which are 

 found in many tissues, notably the liver and spleen, 

 first into complex groupings called nucleotedes, 

 and then into adrenine, guanine, and other 

 bodies. Other ferments subsequently convert 

 adrenine and guanine by a process of deamination 



