PROCEEDINGS AM. PHILOs. Soc. VOL. LI. No. 204

PLATE ||

Normal rabbit: Cerebellum. The average of ten differential Purkinje cell counts from ten rabbits was: Active cells, 64.8 per cent.; fatigued cells, 34.5 per cent.; exhausted cells, 0.7 per cent. [For comparison with cuts on Plate III.]

Frightened rabbit: Cerebellum. The rabbit was frightened once and killed immediately. The average of ten differential Purkinje cell counts from ten such experiments was: Active cells, 83.4 per cent.; fatigued cells 15.7 per cent.; exhausted cells, 0.9 per

Frightened rabbit: Cerebellum. The rabbit was frightened once and killed at the end of two and one half hours. The average of five differential Purkinje cell counts from five such experiments was: Active cells, 55.6 per cent.; fatigued cells, 35.4 per cent.; exhausted cells, 9.0 per cent.

FEAR IN RABBITS.

These cuts and the cell counts as given above illustrate several important points, viz., that cerebral stimulation by fear causes, first, demonstrable morphologic changes in brain cells, second, a marked early increase in the number of active [and hence also hyperchromatic] cells, and, third, that this stimulation is followed by later and more serious morphologic changes in the cells which do not attain a maximum until from 2% to 6 hours have elapsed after the period of fright.