58 G. W. Harris 



of the adrenal glands. Bogdanove and Schoen (9) have recently obtained 

 confirmatory results to the above in the rat. In attempting an explanation of 

 these findings Donovan and van der Werff ten Bosch (23) suggest that 

 anterior hypothalamic lesions damage or destroy some neural mechanism 

 sensitive to the feed-back action of gonadal hormones. It seems clear in adult 

 animals that this feed-back action is exerted on the hypothalamus, and that 

 this structure in turn exerts a restraining influence over gonadotropin secretion 

 by the pituitary gland. A reduced sensitivity of the hypothalamus to gonadal 

 hormone may be one of the changes occurring in the development of sexual 

 maturity, since Hohlweg and Dohrn (57) found that in infantile rats the 

 cytological changes in the pituitary after gonadectomy could be prevented 

 by gonadal hormone in doses approximately one-hundredth of that required 

 in the adult. 



In comparing the experimental findings with the clinical data on cases in 

 which hypothalamic lesions have been found associated with precocious 

 puberty in children (85, 3), two facts are outstanding. Firstly, various lesions 

 (especially hamartomata — a type of congenital abnormality) may result in a 

 greater advancement of puberty in the human than the experimental lesions 

 do in the rat. It is possible, however, that lesions placed in the hypothalamus 

 of fetal rats might yield results more equivalent to those seen in the human 

 in this respect. Secondly, the site of the hypothalamic lesions in clinical cases 

 of pubertas praecox may be well circumscribed and localized, and are often 

 found to be in the posterior part of the tuber cinereum or in the region of the 

 mammillary bodies. Ganong (37) has recently mentioned the results of 

 unpublished experiments by Gellert and Ganong in which lesions just in 

 front of the mammillary bodies of rats have been found to be the most 

 effective in accelerating the onset of puberty. He states that "Lesions in the 

 thalamus and the cerebral cortex also accelerate the onset of vaginal opening 

 to a slight degree, suggesting a non-specific 'stress' effect. . . . However, it 

 should be emphasized that this acceleration is slight when compared to the 

 marked acceleration produced by posterior hypothalamic lesions." 



It is possible that the central nervous system exerts a restraining influence 

 on prepubertal gonadal activity in a wide variety of biological forms. Wells 

 and Wells (86) have found, in the octopus, that blinding by optic nerve 

 section or optic lobe removal, that lesions placed in the subpedunculate/ 

 dorsal basal region of the posterior part of the supraesophageal lobes of the 

 brain, or that interference with the nerve supply to the optic glands, all 

 result in enlargement of the optic glands and gonads. The ovary may enlarge 

 from 1 /500th to as much as l/5th of the total body weight, and may visibly 

 distort the body of the operated animal. Such females may lay viable eggs 

 and brood in a normal manner. Wells and Wells suggest that a neural reflex 

 arc, consisting of the optic nerves-optic lobes-supraesophageal lobes of 

 the brain-and the nerve supply to the optic glands, normally exerts an 



