678 WILLIAM J. ARNOLD 



Results 



The 2,500 r dose to the whole head produced a significant increase in 

 hunger drive between the 20th and 100th days following irradiation. There- 

 after, the difference between experimental and control groups became 

 smaller, until it virtually disappeared. 



The 5,000 r dose to the brain area did not produce a corresponding in- 

 crease in hunger drive. Except for a period 20-30 days after irradiation, 

 when it was slightly higher, the performance of the experimental group was 

 consistently lower than that of the control group. 



The 5,000 r dose to the brain produced a significant decrease in the 

 strength of the thirst drive, a decrease which reached a maximum 30 days 

 after irradiation. At this point, the difference between experimental and 

 control groups was significant. Thereafter, the strength of the drive tended 

 to increase on successive tests, until, at about 75 days after irradiation, there 

 was virtually no difference between irradiated and control groups. 



Motivation — Manipulative Activity 



Subjects were 20 male albino rats exposed to 5,000 r brain area irradiation. 



Mounted on the walls of a hexagonal wooden box 12 in. high and ap- 

 proximately 15 in. in diameter were a horizontal brass bar, a % X H XI /a 

 in. wood block, a wire mesh ladder with three large wooden rungs, a chain 

 attached to a piece of wood % X H X 2 in., a wheel, and a vertical metal 

 pushing panel with a % X H X 2 in. piece of wood mounted near the 

 bottom. A seventh manipulandum, a vertical wooden dowel Yq X 2^ in., 

 was mounted in the middle of the floor of the box. A constant speed poly- 

 graph was used to record automatically any manipulation. 



Fourteen days after irradiation, experimental and control rats were placed 

 one at a time in the box at 5 pm and were removed at 9 am the next day. 

 During these hours, manipulative activity was recorded. This process con- 

 tinued until each rat had had two such periods in the box. Beginning 110 

 days after irradiation, the procedure was repeated. 



Results 



The rats engaged in much manipulative activity, but there were no signifi- 

 cant differences between irradiated and control animals in total manipula- 

 tions or in preferential order for the manipulanda during each of the test 

 periods. 



