An atlas of the chicken hypothalamus was prepared and used for stereotaxic placements of electrolytic lesions. Histological brain sections, showing the location of lesions in the hypothalamus, were prepared, and the locations of the lesions were correlated with physiological and behavioral responses. Photomicrographs of some of the electrolytic lesions that did not evoke physiological or behavioral changes are also presented.

Variations in the head of the chicken resulted in lack of correlation between stereotaxic coordinates and anticipated location of the lesion. Correlation was good, however, between the location of the lesion and physiological response. Multiple physiological responses evoked by some lesions located in approximately the same brain areas in different chickens are described. Occasionally, months after lesioning, disturbed physiological functions were restored to normal, or physiological functions appeared newly impaired.

Results suggest that correlations between lesions (as shown by histological sections) and physiological aberrations cannot be made with confidence for two to four weeks after placement of lesions, possibly because of inflammation, edema, and other reversible brain damage.