GENETIC TYPE AND THE ENDOCRINES 687 



to Met. 120 (positive). The rate of the negative metronome 

 was then increased to 60 beats per minute and presented 

 after a positive C-R of fair strength (8/100 ec. of saliva). 

 Met. 60 evoked no response. This was tried under the same 

 conditions once each day for several days, with the same 

 result. The rate was further increased from 60 to 78 beats, 

 by the above procedure, with complete success. When the rate 

 was advanced to 96, however, it evoked at every application 

 a positive flow of saliva. The limit had been reached. We 

 shall discuss this result later. 



Dog 1030 S , bassethound X Saluki F ,. The salivary condi- 

 tioned reflex was used. The conditioned stimuli were all posi- 

 tive Met. 120; no negative differential stimuli were employed. 

 The aim of the experiment was to study the effect of com- 

 plete thyroidectomy upon the formation of the C-R, and the 

 effect of the subsequent administration of thyroid extract 

 upon the stability of the response. 



This animal was selected because it was evident that, under 

 normal conditions, the salivary C-R could lie formed with 

 comparative ease. The dog exhibited an exceedingly strong 

 general food-taking reaction and was quite manageable in 

 the laboratory, showing little or no evidence of being uneasy 

 or afraid. 



In general this animal was normally playful and alert and 

 was fairly friendly, even with strange people. All reactions 

 towards other dogs were also normal. 



Thyroidectomy was performed, the parathyroids being left 

 intact. Behavior was studied for 1 year and 9 months after- 

 ward. A period of 3 months without tests was allowed after 

 the operation during which time characteristic symptoms of 

 thyroid deficiency appeared. After the general behavioral 

 reactions were clearly affected (without any evidences of loss 

 of appetite or body weight), the conditioned reflex experi- 

 ments were begun. 



The results were clear. No conditioned salivary reflex 

 could be developed. The procedure used successfully with 

 other dogs was carefully followed. The animal, when taken 



