4 CHARLES A. COBURN 



It was found that the Bussey Institute cage was very much 

 more adaptable for the breeders than for testing purposes 

 hence when the mice were weaned they were separated accord- 

 ing to sex and placed in the larger cages and the subsequent 

 tests made from these. Only occasionally, when the number 

 of mice being tested was too great for the supply of large cages 

 were the smaller cages used in this way. 



The food for the mice consisted of cracked corn, oats, sun- 

 flower seed, bread moistened with milk, and occasionally a 

 bit of lettuce or other green food. In the beginning some diffi- 

 culty was experienced in so regulating the food to keep the 

 mice, especially the breeders, in the best condition. The first 

 few months' experience, however, was sufficient to obviate 

 this difficulty. 



The method of testing used by Professor Yerkes was 

 followed in this study as closely as was possible. The mice 

 were classified according to the six grades, namely, 0, 1, 2, 3, 

 4, 5. The grade indicates the absence of all evidences of 

 wildness or savageness, and the grade 5 indicates the presence 

 of all the various signs of wildness or savageness in the greatest 

 number and intensity. After a few mice were tested definite 

 standards which represented the various grades were fixed 

 and there is fairly definite evidence to indicate that these 

 standards were adhered to throughout the investigation. Every 

 few weeks an additional test was made of several mice which 

 had been tested a day or two previous along with so great a 

 number that it would be impossible to remember the grade 

 of any mouse. In making these check tests the mice were 

 taken at random from the different cages and after testing 

 them a comparison would be made of the results of this test 

 and the one immediately preceding. The grading varjed 

 occasionally but rarely more than one grade. The results 

 given below were chosen at random and are typical of such 

 tests. 



The mice were weaned, given their initial test and numbered 

 when they were about five or six weeks old. The age varied 

 somewhat in order to allow several litters to be grouped and 

 thus facilitate the work. At this age the mice are not full- 

 grown but they have full use of all their organs of sense and 

 are very active. 



