REl'RODUCTIV^E BEHAVIOR '233 



FIG. 6. Sites of hypothalamic lesions in the female rabbit brain. Mammillary lesions at 

 6 [stippled] abolished mating behavior in spite of therapy with e.xogenous estrogen but did not in- 

 duce ovarian atrophy. Tuberal lesions at A (solid black) blocked copulation-induced ovulation or 

 led to ovarian atrophy but did not diminish receptivity if extrinsic estrogen was supplied. [From 

 Sawyer (79).] 



latter sites of local damage perhaps correspond to the 

 anterior hxpothalamic lesions of Brookhart & Dey 

 (15) which irreversibly eliminated sex behavior in the 

 male guinea pig without damaging the testes. 



Sexual precocity of cerebral origin may result from 

 lesions such as tumors originating within the hypo- 

 thalamus or damaging hypothalamic areas from 

 above, as in the case of pinealomas (7). Accelerated 

 sexual development through increased gonadotrophic 

 secretion may not he accompanied by precocious 

 sexual behavior, a further indication that gonado- 

 trophic and sex behavioral centers are not identical. 

 Hillarp et al. (48) have described preoptic lesions in 

 rats of either sex which temporarily stimulate compul- 

 sive male mating behavior. Harris and his colleagues 

 have suggested that the anterior hypothalamus in 

 ferrets and rats contains a center inhibitory to the 

 release of pituitary follicle stimulating hormone (24, 

 25, 46). Lesions in this area accelerate the onset of 

 seasonal estrus in mature ferrets and the opening of the 

 vaginal orifice in young rats. 



Effects of Nerve Lesions on Maternnl Behavior 



No systematic studies have been made of the 

 effects of nervous lesions on maternal behavior except 

 in the rat. Female rats rendered anosmic and deaf bv 

 Wiesner & Sheard (96) still built nests and retrie\ed 

 young. More recently Beach & Jaynes (14) have 

 shown that rat maternal behavioral responses sursive 

 enucleation of the eyes, reinoval of the olfactory bulbs 

 or destruction of sensory nerv-es to the snout. Re- 

 moval of all three afferent pathways, howe\er, com- 

 pletely inhibited maternal care of the young, and the 

 combined destruction of any two sensory routes 

 seriously interfered with maternal behavior. 



In 1937 Beach (11) reported that removal of more 

 than 30 per cent of the cerebral cortex delays nest 

 building in the pregnant rat and subsequently de- 

 creases its ability to retrieve and care for its litter. 

 Stone (90) and Davis {20) confirmed the finding that 

 large cortical lesions interfered with maternal be- 

 havioral performance. All of these investigators 

 stressed the relationship between the size of the lesion 



