GENETIC TYPE AND THE ENDOCEINES 649 



The classic conditioned reflex method was used. The pro- 

 cedure in general was to study the conditioned reflexes in a 

 particular dog both before and after critical alteration of the 

 internal secretions. 



A group of pedigreed hybrid animals, the majority of which 

 were second generation (F 2 ) from the cross between the 

 German shepherd and the bassethound, were selected for the 

 tests. These animals were more or less uniform in body build. 

 The conditioned salivary reflex was formed in one group and 

 the conditioned motor or defensive reflex in another. Before 

 the disturbance or modification of the gland was induced, 

 conditioned reflexes were stabilized in each animal for about 

 1 year in order to obtain as control a series of responses 

 reasonably stable and uniform in character. The same kind 

 of observations were continued after the disturbance for 

 as long a time as feasible. 



The conditioned reflex method is especially advantageous 

 in experiments of this kind since not only can both the salivary 

 and the motor conditioned responses be recorded graphically, 

 but they can be measured for intensity with a high degree 

 of accuracy. This technique is of special advantage in show- 

 ing the most delicate and refined details of the behavioral 

 pattern in animals whose glandular functions have been 

 altered. However, we are also fully aware of the great im- 

 portance of the simpler methods in observing animal be- 

 havior. Carefully ''watching" what the animals are capable 

 of doing has great value, and we have made it a practice to 

 record descriptive notes of general behavior as a supplement 

 to the data of the conditioned reflexes. 



The general arrangements of the laboratory for the con- 

 ditioned reflex studies are shown in plate 106. Two rooms 

 were necessary, one for the investigator, from which the 

 stimulations were applied and controlled and in which the 

 conditioned reflexes were recorded and registered, and a com- 

 pletely separate but adjoining sound-deadened animal 

 chamber. The dog's movements are easily observed from the 

 apparatus room through a small reducing lens fitted into an 



