THE PARATHYROID GLANDS 



545 



They made an extensive series of experiments on the action of guani- 

 din hydrochloride and methylguanidin nitrate on the cat, rat, and rabbit, 

 and in all of these the symptoms produced were indistinguishable from 

 those of the tetany following parathyroidectomy. Fig. 7 shows the trac- 

 ing taken from a cat after the intramuscular injection of guanidin hydro- 

 chloride. The electrical reactions of the peripheral nerves were measured 

 and found to correspond with those obtained in parathyroid tetany. 



They tested the action after section of the spinal cord and after spinal 

 section followed by decerebration, and found that the absence of tone in 

 the hind limbs after section of the cord and the persistence of the symptoms 

 after decerebration were similar to the results obtained following the same 



Fig. 7. Tracing of tremors of hind-legs of cat after guanidin. (Noel Paton and 

 Findlay.) 



procedures in animals with parathyroid tetany. They injected guanidin 

 into the subdural space and found that in small doses it excites the cord, 

 as in tetany, but in larger doses it has a depressant action. The actions of 

 guanidin and methylguanidin were antagonized by calcium lactate, and it 

 was also shown that latent tetany in the early stages of parathyroidectomy 

 could be transformed into active tetany by the administration of a dose of 

 guanidin insufficient to produce any effect in the normal animal. 



The elements acted on peripherally by guanidin, viz., the nerves or 

 nerve endings, are the same as they found to be affected in parathyroid 

 tetany. After parathyroidectomy the electrical excitability of the per- 

 ipheral nerves is not always proportionate to the severity of the symptoms, 

 and after the administration of guanidin the peripheral nerves may not 

 be influenced at once. 



As a matter of fact, the symptoms are rarely so violent in parathyroid 

 tetany as after the injection of guanidin, since probably when developed in 

 the body the concentration is not so great. Another point of interest is the 



