722 O. D. ANDERSON 



stood, with the lowering of general metabolism occurring 

 at the time, and which may be due to an impairment of thyroid 

 function. To test how far such a view is tenable we tried 

 restoring the weakened C-R by administering thyroid extract 

 and were partially successful. Previous observations by many 

 workers in the field of endocrinology had indicated that re- 

 moval of the pituitary is followed by atrophy of the thyroid, 

 and that this in time brought about a lowering in general 

 metabolism. 



Assuming that the lessened efficiency and magnitude of 

 the conditioned reflex in a hypophysectomized dog is due 

 alone to absence of the anterior lobe, we were able to build 

 a reflex in an animal from which the posterior lobe had 

 previously been removed. Since the posterior lobe was re- 

 moved while this animal was young, and since there was no 

 difference between his performance in the C-R tests and 

 those of normal dogs in the training period, we conclude 

 that the tremendous reductions in C-R values after complete 

 pituitary removal resulted from the absence of the secretion 

 of the anterior rather than the posterior lobe. 



In summary, the tests were as follows. Two dogs were 

 completely hypophysectomized and from a third dog only 

 the posterior lobe of the gland was removed. One of the first 

 two dogs was tested with both salivary and motor reflexes, 

 the other was trained in the salivary C-R only. In both types 

 of reflexes the efficiency and magnitude of the C-R were 

 reduced to zero. The administration of extract of the ante- 

 rior lobe revived the reflexes to some extent but this effect 

 was transitory. The subsequent administration of both ante- 

 rior and posterior pituitary extract together had practically 

 no restorative effect. In one of the dogs, administration 

 of thyroid extract raised the efficiency of the reflex to a 

 value above that which resulted from the anterior pituitary 

 extract, and almost to normal level. Finally, in this same 

 animal, a succession of pituitary transplants were made. 

 Following each transplant the efficiency and the magnitude 

 of the reflex did not rise as high as under the thyroid ad- 



