OLFACTORY BULBS OF THE ALBINO RAT 215 
age than normal brains of seventeen days (The Rat, table 74). 
Rats seventy-seven days old had brains weighing practically 
the same as those of normal female rats of forty-two days. 
Bulbs of rats twenty-four to fifty-three days old, actually 
weighed only 70 per cent as much as those of normal rats of 
thirty days (table 2) and only 52 per cent as much as bulbs of 
normal rats eight weeks old (table 4). 
Rats eleven weeks old (table 11) gave bulbs of the same abso- 
lute weight as those of control rats of thirty days (table 2). 
In both cases the olfactory bulbs formed a smaller per cent of 
the total brain weight than appeared among the controls of 
like age in Series A, as the following arrangement of the data 
shows: 
TABLE 9 
PERCENTAGE 
GROUP AGE WEIGHT OF 
OLFACTORY BULBS 
days 
Maile Ose. sana. Test rats, defective diet- 
Series B. 24-53 33, 11a 
Mable as4. 028s: Control. 30 3) 4 
Ho) Kee [Ree Test rats, defective diet- 
Series B 77 3.48 
May lewa ne Fo. - Control 60 3.99 
Meatblen Gienasecie.. Control 79 4.16 
The details for these series are given in tables 10 and 11 which follow. 
4. Series C. Sick rats 
In the course of the experiments a number of sick rats came 
under observation. Eleven of these were examined to determine 
whether the brain, and especially the olfactory bulbs, showed any 
effects of the diseased condition. Three of these rats were the 
sole survivors from a group of twelve attacked by a serious 
bowel trouble which killed the other nine occupants of the cages. 
At the time of the onset of the illness, the rats were about eighty 
days old. After about ten days, these three seemed to recover 
and were kept until they were about a hundred and thirty-five 
