GENETIC TYPE AND THE ENDOCRINES 697 



The results are interpreted to mean that a decrease in, or 

 an absence of the thyroid secretion results in a lowering of 

 the general level of excitability. This lowering also accounts 

 for the apparent improvement in the discriminating ability 

 of the animals, as explained above. 



The Effect on Behavior of the Administration of 

 Parathyroid Extract to the Normal Dog 



Dog C-19 , bassethound X shepherd F 3 . The salivary C-R 

 was used. The conditioned stimuli were Met. 120 (positive) 

 and Met. 28 (negative). The dog was trained for 6 months 

 before the critical tests. 



The general behavior picture of this dog was that of the 

 well balanced type, friendly and cooperative, and with no 

 trace of shyness. She had been born and reared in the lab- 

 oratory and handled a great deal, and proved to be an in- 

 telligent and extremely versatile animal. 



The C-R was formed very rapidly, in five trials, and there- 

 after appeared with a high degree of regularity. The mag- 

 nitude of the response was remarkably uniform from one 

 test period to another. For these reasons, the animal was 

 used not only in this experiment but also in others, in which 

 the effects of the administration of anterior lobe pituitary 

 extract and of adrenalin on the normal dog were studied ; 

 and in a later experiment, this dog was used to study the 

 effect of hypophysectomy. 



Parathormone (Collip), 5 units daily, was administered for 

 20 days. The C-R tests were carried out each day, 4 hours 

 after the injection. The positive C-R was altered appreciably. 

 Both the efficiency and the magnitude of the response 

 increased. 



Table 15 shows that the percentage of correct responses 

 to Met. 120 increased slightly during administration of the 

 extract (86 per cent to 88 per cent), and increased afterward 

 to better than normal (to 100 per cent). The negative re- 

 sponse became somewhat less efficient (33 per cent to 25 

 per cent) and afterward continued to decrease (to per cent). 



