GENETIC TYPE AND THE ENDOCRINES 679 



and body movements, respiration and strong reflex flow of 

 saliva during the Met. 120. Figure 6, after the operation, 

 shows the absence of head and body movements, the slow, 

 regular breathing, and the absence of the flow of saliva 

 during the same stimulation. In both records the reactions 

 to food itself are normal. 



EFFECT Of THYROIDECTOMY 



AND OF THE SUBSEQUENT ADMINISTRATION OF THYROID EXTRACT 



ON THE CONDITIONED SALIVARY REFLEX 



#gU l = ADM.rmr«Ai-,o« of £ cm 



TtiyRO.D EXTRACT DAIL/ 



J , Lj-J 



I THYPIDLC T OMTZ E 



FORMAL I THY ROlDECTOMl ZED 



Text-figure 120. Chart showing the effect of thyroidectomy and of subsequent, 

 administration of thyroid extract on the conditioned salivary reflex in dog 866. 

 Note the almost complete collapse of the reflex following the thyroidectomy and 

 its subsequent revival, almost to normal magnitude, by thyroid extract. When 

 the extract is withdrawn, the reaction tends to diminish and disappears completely 

 within 2 months after withdrawal. 



In text-figure 120 the magnitude of the positive salivary 

 C-R is shown during all the phases of the experiment. The 

 almost complete disappearance of the response after thyroid- 

 ectomy is followed by an enhancement of the C-R within 10 

 days after the thyroid treatment was begun. This enhance- 

 ment continued throughout the treatment and for nearly a 

 month after it was stopped, then the C-R again collapsed. 



The length of the latent period of the C-R indicates the 

 degree of alertness. In this thyroidless dog, the enormously 

 lengthened latent period indicates the retardation of higher 



