GENETIC TYPE AND THE ENDOCRINES 529 



two groups of dogs differ not only in general alertness, but 

 also in mode of walking, orienting, and in voice. These dogs 

 have been considered as normal physical types. Other types, 

 however, have abnormal physical tendencies, as for example 

 the giant St. Bernard and great Dane, which also have char- 

 acteristic behaviors. Again there are midgets among the dog 

 breeds, as among humans, and these likewise have definite 

 behavioral tendencies. The active nervous nature and high 

 voice of the Pomeranian poodle are suggestive of certain 

 performances of human midgets. Some dogs are known for 

 their friendly aggressiveness, and still others for their inde- 

 pendence. 



Just as the study of physical form and glandular condi- 

 tions among the dogs was based on animals showing the 

 widest differences in these characters, so a study of behavior 

 can best be analyzed by using animals showing the widest 

 differences in behavioral characteristics. It is among these 

 types that the specific behavioral qualities are most easily 

 differentiated. 



Method. The program of research reported here involved 

 a comparison of the performances of a large number of dogs 

 whose reactions were observed in the same situation from 

 day to day. Needless to say, the control of the situation and 

 the method employed were of utmost importance. The ex- 

 perimental environment had to be the same for each dog, 

 and the performance, considered as a sample of what the 

 organism was doing, had to involve the same reaction systems. 

 The conditioned reflex method, used throughout these experi- 

 ments, offered an accurate control of these factors. In this 

 method the performance of one effector, whether it be the 

 salivary gland or a group of muscles, is the focus or center 

 of the behavior under observation. This performance serves 

 only as the basis of interpretation of what the organism is 

 doing. It has already been shown in the experiments of 

 Pavlov that this method emphasizes behavior differences 

 among dogs. Although Pavlov ('27) indicated some of these 

 differences, he placed no emphasis on their relationship to 



