GENETIC TYPE AND THE ENDOCRINES 539 



In line with the studies of Pavlov, dogs have been classified 

 as inhibitable or excitable, depending on their reaction under 

 experimental conditions, and the terms excitation and inhibi- 

 tion have been used to apply specifically to action of the 

 nervous system. Our observations are in agreement with the 

 findings that dogs classify themselves into two widely dif- 

 ferent behavioral types, but the terms used to designate each 

 group should refer to a general configuration of the total 

 organism rather than to nervous action alone. The excitable 

 dogs, as will become clear in the present work, not only have 

 a more intense nervous action than the inhibited dogs, but 

 there are indications that all their bodily processes are more 

 intense in nature. An example of this is their higher metabo- 

 lism. In the present experiments, therefore, the dogs will be 

 designated as highly active and extremely lethargic types. 

 For purposes of convenience and clearness, the lethargic class 

 will be called group A, while the highly active will be classified 

 as group B. The dogs falling between these polar types 

 will be classified as intermediates and indicated as A-plus 

 and B-minus, signifying that they are nearer the A or B polar 

 group yet show certain differences which prevent them from 

 being classified in these groups. At present our interest is 

 in behavior rather than breed, and for this reason the types 

 of behavior isolated will be discussed without emphasis on 

 the breed of dog characteristic of each. 



CHARACTERISTICS OF THE LETHARGIC MODE OF PERFORMANCE, 



GROUP A 



A total of fifty-two animals have been studied in the ex- 

 periments, and of this number thirty-nine were trained in the 

 conditioned food taking situation. Of the thirty-nine trained, 

 thirty-six were able to make a satisfactory adjustment. Eleven 

 of these fall into the sluggish and inactive group, including 

 the following : four bassethounds, 1426 $ , 1427 $ , 83 $ , and 

 219 $ ; two dogs which were predominantly dachshund in in- 

 heritance, 335 9 and 148 $ ; two dachshund-Boston terrier FjS, 



