CHARLES H. SAWYER 



167 



level just above the threshold for inducing subcortical seizures is ineffective in 

 activating the pituitary (0/5 ovulated) while similarly gauged stimuli applied 

 to medial amygdaloid nuclei are at least partially effective in triggering the 

 release of ovulating hormone (3/5 ovulated). The medial nuclei project via the 

 stria terminalis to the ventromedian nucleus of the hypothalamus (12). These 

 experiments are continuing, and again the precise positioning of stimulating 

 electrodes awaits histological confirmation. 



Relatively immense lesions in the rabbit central and peripheral nervous 

 systems (5) have been ineffective in blocking copulation-induced ovulation. 

 These include anesthetizing or removing the proximal half of the vagina, all 



Fig. 2. Sites of hypothalamic lesions in rabbit brain. Lesions at base of ventromedial 

 nucleus in cross-section A blocked copulation-induced ovulation. Lesions in medial mam- 

 millary nuclei at cross-section B (stippled) blocked mating activity in spite of added extrinsic 

 estrogen and maintenance of well-developed ovaries. Tracings from the rabbit atlas (34). 



of the uterus, cutting or removing the lumbosacral cord, the abdominal sympa- 

 thetics, the eyes, olfactory bulbs, middle ear or neocortex. On the efferent side, 

 removing the cervical sympathetics (18) or the greater superficial petrosal nerve 

 (41) failed to block, but cutting the pituitary stalk (6) did interrupt the copula- 

 tion-ovulation sequence. 



In our laboratory (31) recent surgical or electrolytic lesions have bilaterally 

 severed or destroyed in each of five rabbits the olfactory bulbs, orbitofrontal 



Fig. I. Five minutes of continuous EEG record from cat medial hypothalamus (A) and 

 lateral hypothalamic area (B) in the region of the medial forebrain bundle. Period of artificial 

 stimulation of the vagina is underscored in the first line. Recurrent periods of high amplitude 

 slow waves are apparent in B. 



