Watson, Weight of the Nervous System. 5 1 7 



rats in these litters were of good stock, strong, healthy, and 

 large for their age. 



In the following description of results, these five groups 

 are referred to under the letters A, B, C, D, and E. At the 

 beginning of the experiments 



Group A contained 5 female rats 



" B "3 



« C "4 " " 



" D "4 



" E "5 " " 



Total 21 



Each of the above-named groups, at 70 days of age (the 

 age at which sexual maturity is reached), was divided into ap- 

 proximately equal sub-groups, one containing the rats which 

 were to be mated, the other, those which were to remain un- 

 mated. 



Since we desired to make the condition for growth as near- 

 ly ideal as possible, we fed the rats used in this experiment 

 very carefully, giving them always a rich and varied diet. 

 Baker's bread, softened with unskimmed milk, was the chief 

 article of food. Since food of this character is likely to sour if 

 left in the cages, only so much of it was given as could be con- 

 sumed by the rats from one period of feeding to the next. 

 Sunflower seed and cracked corn were always kept in the cages. 

 Vegetables and meat were given once a week. Great care was 

 taken to avoid surfeiting the rats. They were fed each morn- 

 ing between nine and ten o'clock. 



The rats were weighed once a week, and weighing came 

 always before feeding. 



The experiment was conducted in a warm, sunny room, 

 the temperature of which was kept constantly above 70° Fah- 

 renheit. 



At 70 days of age^ the rats destined to bear young were 



'At this age the average weight of the unmated rats approximately equalled 

 that of the mated. A slight difference, however, existed in favor of the mated 

 rats (2 gr. heavier on the average). 



