8 CHARLES A. COBURN 



caught. Often the wildness is sufficiently great that the mouse 

 apparently forgets to hide in the nest at the first move to open 

 the door of the cage, or it may have hidden there but at the 

 first touch of the hand on the outside of the nest it will jump 

 from the nest and begin to run frantically about the cage arid 

 finally try to hide in the upper far corner of the cage or it may 

 continue to run about the cage until caught. When one with 

 such wildness is caught it continues to try to escape, jumping 

 about the hand and trying energetically to pull its tail loose. 

 After some time it may become quiet but will immediately 

 resume the attempts to escape at the slightest move of the ex- 

 perimenter, especially if the pressure of the fingers on its tail 

 is somewhat lessened. 



3. Squeaking. This was rarely observed except in very 

 young mice or older mice when they were being graded for 

 the first time. However it is included as an indication of 

 wildness since it was never observed in tame mice. 



4. Urination and defecation. Both of these are associated 

 with the greater degrees of wildness. They were used in grading 

 only in a general way. 



5. Jumping from the hand when released and immediately 

 hiding in the nest or excitedly running about the cage. When 

 a very wild mouse is being put back in the cage it will imme- 

 diately jump from the hand the instant the pressure on its tail 

 is released. It usually jumps straight ahead no matter whether 

 that is toward the top, side or front of the cage, or directly 

 through the door of the cage toward the experimenter. If it 

 alights in the cage it generally dashes toward the nest and hides. 

 At other times it may run about the cage but sooner or later 

 will seek the nest. A tame mouse will never jump in this way. 

 It will go to the edge of the hand and look down. If the dis- 

 stance is very great it will try the other side and will not of its 

 own accord leave the hand unless it can reach the floor with 

 its fore feet when it hangs over the side of the hand. When it 

 is safely back in the cage it makes no attempt to hide. 



Professor Yerkes found that there are two kinds of savage- 

 ness in rats. These he termed defensive and offensive. Only 

 the former is found in mice. The most savage mouse will 

 never attack the observer nor make the slightest move to do 

 so. It will only bite when it is caught and unable to get loose. 



