20 GARDNER CHENEY BASSET 



quired by them to learn the maze had led the investigator to 

 suspect a less than normal brain weight; and, when the brains 

 were weighed, this was found to be the case. Table III presents 

 a comparative summary consisting of the daily averages of the 

 nine rats containing B blood and of the twelve control rats 

 lacking it. Eight of the rats containing B are one-half C and 

 one-half B; the remaining rat is one-half C, one-fourth E, and 

 one-fourth B. That the C blood is not a factor in their erratic 

 behavior is proven by the fact that most of the rats of the co- 

 trol series not containing B blood do also contain C. In order 

 to compare the behavior of control rats having B and those 

 lacking it with that of the inbred rats, cross reference may be 

 made from Table III to the inbred averages of Table I. The 

 control rats having B blood shall be referred to in Table III 

 as Control -fB; those lacking B blood as Control • — B. 



The tables (I and III) show that two of the inbreds and one 

 of the -fB failed to learn the maze; the — B controls had all 

 learned at the end of the twenty-fifth day. The inbred rats 

 required, on the average, 36.62+ days to learn; the -fB 35.67-}- 

 days, and the — B but 16.42 days. The absolute retention of 

 the inbreds was, on the average, 81.558 seconds; of the -fB, 

 72.475 seconds; and of the — B, but 51.083 seconds. Two of 

 the inbreds failed to relearn; all the -f B had relearned at the 

 end of the twenty-second day; while all the ■ — B had relearned 

 at the end of the eighth day. The inbreds required, on the 

 average, 12.68^ days to relearn; the +B, 8.24 days; the — B, 

 but 4.08 days. 



In these criteria of ability to learn the maze, the inbred rats 

 did the least well; the -fB rats were, in each instance, above, 

 but not far from, the record of the inbreds; the — B were much 

 superior to either. 



Both body length and body weight were greatest in the in- 

 breds, next in the +B, and least in the — B. Actual brain 

 weight was least in the inbreds, much greater in the +B, and 

 sHghtly greater in the — B than in the -f B. The relative brain 

 weight (in reference to body length) of the inbreds was 5.46% 

 less than that of the — B; that of the -f B was 2.53% less than 

 that of the — B. The relative brain weight (in reference to body 

 weight) of the inbred rats was 10.02% less than that of the — B; 

 that of the -f B was 5.15% less than that of the — B. As might 



