708 O. D. ANDERSON 



occasion after the operation was this dog known to bark. 

 The appetite was poor at times, but there was no loss in 

 body weight. 



Due to the inherent difficulty in separating the function of 

 the parathyroid from that of the thyroid, one cannot definitely 

 say that these results are due to disturbance of the para- 

 thyroid alone. But since the administration of parathyroid 

 extract (in both dogs) had a restorative effect on the re- 

 sponses, it is reasonable to suppose that this restoration, 

 though not complete, was due in part to the presence of the 

 parathyroid substance. As a result of the operation the level 

 of excitation was lowered in the same way as in the absence 

 of the thyroid. In the one case (parathyroid) the disturbance 

 in calcium may be the chief factor in producing the alteration 

 in nervous irritability, and in the other case (thyroid) the 

 alteration in excitability is unquestionably associated with 

 the lowering of the rate of general metabolism. 



As after thyroidectomy, the efficiency of the negative re- 

 actions increased after the parathyroid operation. Also as 

 with the thyroid, this increased efficiency of the negative 

 after the operation is associated with the general lowered 

 responsiveness or excitability. Not only is the responsiveness 

 to the C-R below par, but the dog is also unresponsive to 

 stimulation in general. As was pointed out, the animal failed 

 to respond even to a shock applied to his leg or when pinched 

 by a steel forceps. 



It is interesting that there is an obvious lowering of the 

 level of excitability in a dog just before going into tetany. 

 At first consideration, such results may be considered in- 

 consistent. It must be remembered, however, that prior to 

 the attack the animal's responsiveness is externally aroused 

 (by stimulation), whereas in the tetanic attack external stimu- 

 lation is not being tested. The hyper-irritability in tetany is 

 expressed as an incoordination of the neuro-muscular system, 

 which is due to a disturbance in the function of the motor 

 cortex. The unresponsiveness before tetany and the tetany 

 itself are related to the same disturbance in internal chem- 



