743 



ment of the C-R following the administration of various 

 extracts was in almost every case greater when the extract 

 was given to a dog from which the gland had been removed 

 than when given to a normal, unoperated dog. The greater 

 the physiological need for the substance, the greater its 

 effectiveness when introduced. 



All extracts used exerted approximately the same kind of 

 influence upon the positive C-R. They were uniformly fol- 

 lowed by an increase in the magnitude of the response. 

 This enhancement was greater after injection of some extracts 

 than others. The greatest increase in magnitude of the reflex 

 followed anterior lobe pituitary extract and the least followed 

 adrenalin. The poor record for adrenalin is due to the fact 

 that it produces an increase followed by a decrease, and in 

 the average the two phases almost completely counter-balance 

 one another. The constancy of the reflex was only slightly 

 affected by any of the extracts. The extracts are listed in 

 table 35 in the order of their effects. Each figure represents 

 the average values for two dogs, except for the anterior 

 pituitary extract, which represents one dog. 



TABLE 35 



Changes in the positive C-B following the administration of extracts 

 in the unoperated dog 



Anterior pituitary extract increased the constancy of the 

 response somewhat (14 per cent), while the other substances 

 had almost no effect upon the constancy of reaction. The 

 negative stimuli were not used in many cases during the 

 experiments on the administration of extracts for the reason 

 that the substances were given early in the training period, 

 prior to the attempts to form differentiations between positive 



