668 



O. D. ANDERSON 



reflex values were slightly higher than normal for 8 days 

 after the treatment was discontinued, and then showed a 

 marked decrease. 



After the injections were started the dog became definitely 

 more nervous, showing restlessness and general hyper-irri- 

 tability as he was being prepared for the day's testing. When 

 led upon the platform he would crouch and tremble, lower 

 his ears and suddenly turn his head about in all directions. 

 After the straps were loosely placed about the forelimbs, and 



DOG * 



EFFECT OF THYROID EXTRACT UPON 

 THE CONDITIONED MOTOR REFLEX 

 IN A NORMAL DOG 



pOng = ^Wfrttmstrjtien 

 of / gm. thyroid cyi'nc't 



di//y /&r Jf </iy5 



Text-figure 117. The effect of thyroid extract on the conditioned motor reflex 

 of dog 868. Note the increase in the magnitude of the reflex during the admin- 

 istration of the extract and its subsequent diminution after the extract was 

 withdrawn. 



the experimenter turned to leave, the dog attempted to ex- 

 tricate himself, first by trying to step out of the straps, 

 then by lunging against them. The straps had to be securely 

 fastened. The restlessness during the interval between one 

 stimulation and the next showed definite characteristic form. 

 Being confined within a narrow area, the animal did not 

 struggle as violently as during the preparation period, but 

 continually raised the reaction leg in small, jerky movements. 

 Sometimes the leg movements were directed toward shifting 

 the body position slightly forward, or back, or to the side, 



