HABIT FORMATION IN ALBINO RATS 9 



the case with the normal controls. The relative brain weight 

 (in reference to body length) of the inbreds is 4.43% less than 

 that of the normals. The relative brain weight (in reference 

 to body weight) of the inbreds is 7.99% less than that of the 

 normal control. The percentage of water in brain and cord 

 normally decreases with age ; but in the inbreds used in the maze 

 experiment, although killed, on the average, fourteen days later 

 than the control rats, the percentage of water was greater. 



The figures presented in Table I support the hypothesis that 

 a less than normal average brain weight in a strain of rats is 

 accompanied by an average lesser ability to form habits. 



TABLE la 



The Maze 



Daily Learning Averages of Inbred and Normal Control Rats 

 (Time in seconds) 



Day 1 Day 2 Day 3 Day 4 Day 5 



Inbred Average 531.665 91.404 68.160 39.459 25.568 



Control Average 505,128 110.739 53.851 28.404 25.613 



Day 6 Day 7 Day 8 Day 9 Day 10 



Inbred Average 20.015 13.899 11.061 9.709 9.522 



Control Average 17.366 13.381 11.994 12.440 9.619 



Day 11 Day 12 Day 13 Day 14 Day 15 



Inbred Average 10.217 7.937 8.708 7.600 7.000 



Control Average 7.295 7.748 7.354 6.904 7.277 



Day 16 Day 17 Day 18 Day 19 Day 20 



Inbred Average 6.439 6.585 6.305 6.492 6.458 



Control Average 6.687 6.428 5.900 6.209 5.851 



Day 21 Day 22 Day 23 Day 24 Day 25 



Inbred Average 6.362 5.749 5.978 5.753 6.248 



Control Average 5.630 5.816 5.710 5.675 5.420 



Day 26 Day 27 Day 28 Day 29 Day 30 



Inbred Average 5.734 7.130 5,669 6.387 5.697 



Control Average 5.389 5,442 5.479 5.496 5.437 



Day 31 Day 32 Day 33 Day 34 Day 35 



Inbred Average 5.384 5.708 5.702 6.084 5.731 



Control Average 5.700 5.502 5.378 5.499 5.308 



Day 36 Day 37 Day 38 Day 39 Day 40 



Inbred Average 5.590 5.476 5.494 5.540 5.848 



Control Average 5.272 5.249 5.327 5.363 5.316 



Day 41 Day 42 Day 43 Day 44 Day 45 



Inbred Average 5.640 5.978 5.631 5.526 13.456 



Control Average 5.343 5.573 5.375 5.250 5.444 



