742 O. D. ANDEKSON 



allowed to progress, since it was feared that the animals 

 might succumb. Many of the C-R tests were made when the 

 animal was in a state of medium parathyroid deficiency, so 

 to speak. It will be recalled that when dogs were allowed 

 to present symptoms of very marked deficiency of para- 

 thyroid hormone, the conditioned and other responses were 

 entirely obliterated. The decrease in the constancy and the 

 magnitude of the C-R following castration was small when 

 compared with the enormous decreases following the other 

 operations. 



In the majority of cases in which a negative differential 

 stimulus was tried, the number of correct (zero) responses 

 in the post-operative periods increased as the number of 

 correct positive responses decreased. The percentage of the 

 increase in the negative reactions for each operation are 

 tabulated in table 34. 



TABLE 34 



Percentage of the increase in the constancy of the negative C-B 



following the operations 



Thyroidectomy 53% 



Hypophysectomy 47% 



Ovariectomy 3 7 % 



Thyro-parathyroidectomy 6% 



The increase in the constancy of the negative C-R was 

 quite considerable in the case of the first three operations 

 listed, but was very slight following thyro-parathyroidectomy ; 

 indeed, one of the dogs, 869, showed a 50 per cent decrease in 

 the constancy of the negative following the latter operation. 

 The negative C-R was not used with the adrenalectomized 

 dog. 



The results obtained by administering the different gland 

 substances to normal dogs were not so striking as those 

 following the removal of the glands. This, of course, was to 

 be expected, since imbalance of the internal chemistry is 

 undoubtedly far less extensive and critical following the ad- 

 ministration of secretory material than as a consequence of 

 removal of part of the glandular mechanism. The enhance- 



