6 CHARLES A. COBURN 



grasp the tail and hold it only until it could be grasped by the 

 fingers of the left hand whereupon the removal would proceed 

 as usual. It is to be noted that the forceps were used as little 

 as possible since the chance of unconsciously using unnecessary 

 pressure was much greater with the forceps than with the fin- 

 gers. The mouse was allowed to remain on the palm of the 

 hand for a moment while a definite impression of its behavior 

 was obtained. Then with the tail between the thumb and 

 forefinger of the right hand and the mouse on the palm of the 

 left or being gently held in the left hand the sex would be de- 

 termined. This done the mouse would be returned to the 

 position on the palm of the right hand and one of the fingers 

 of the left hand or a pencil would be moved fairly rapidly up 

 and down just before the mouse, the experimenter at the same 

 time making a clicking sound with his tongue and teeth. The 

 object of this was to get the behavior of the mouse when excited 

 if such was possible. This completed the testing observations 

 in the case of the initial tests and, the judgment being made, 

 the result was thereupon entered. In the subsequent tests 

 the behavior of the mouse when released was noted before 

 making the judgment. The mouse was then numbered and 

 placed in a cage with others of like sex and, as nearly as possible, 

 like age in order to prevent promiscuous breeding and the 

 killing of the younger mice by the older. 



The system of numbering was identical with that in use at 

 the Bussey Institute. It consisted in making certain notches 

 or holes in the ears of the mouse. When viewed from behind 

 the number indicated on the right ear represented the units 

 and that on the left ear the tens of any particular number. 

 Absence of any mark indicated zero. 1, 2, 3, etc. were re- 

 spectively designated as follows: hole in the upper side of ear, 

 hole in outer side, hole in lower side, notch in upper edge, notch 

 in outer edge, notch in lower edge, notches in upper and outer 

 edges, notches in outer and lower edges, notches in upper and 

 lower edges. Ten was indicated by a hole in the upper side 

 of left ear and nothing in the right ear, 22 by a hole in the outer 

 side of both left and right ears, etc. The wounds thus made 

 were usually observed to be completely healed in a very few 

 days. By such combinations any number up to and including 

 99 could be indicated. As the different hundreds were desig- 



