GENETIC TYPE AND THE ENDOCBINES 



741 



and further to the fact that these materials cannot be sup- 

 plied to the body in the normal physiological amounts or 

 manner. 



The alteration in responsiveness is not necessarily due 

 directly and primarily to the absence or excess of the secretory 

 principle of the gland in question. The observed effect may 

 well be secondary to some primary disturbance induced by 

 the giand modification which the experimenter induced. The 

 experiment in which the salivary C-R was obliterated follow- 

 ing 1 hypophysectomy and later more completely revived by 

 thyroid than by anterior pituitary extract bears upon this 

 point. The diminution in response in such a case may have 

 been due more directly to regressive changes in the thyroid 

 and its secretion following the hypophysectomy than primarily 

 to the loss of anterior pituitary secretion itself. 



The constancy and the magnitudes of the positive condi- 

 tioned reflexes were impaired to various degrees following 

 endocrine ablations, most complete after hypophysectomy 

 and least following removal of the gonads. The several opera- 

 tions are listed in table 33 in the direct order of the magni- 

 tudes of the ensuing effects. The figures represent the average 

 values from the two or more animals concerned in each 

 operation, except for adrenalectomy, where only one dog is 

 recorded. 



TABLE 33 



Percentage of decrease in the positive CI,' following operation* 



CONDITIONED REFLEX 



Almost the same degree of impairment resulted in the 

 case of the first three operations. The figures for the thyro- 

 parathyroidectomy indicate a somewhat lesser effect because 

 of the fact that the deficiency of the parathyroid was not 



