Ontogeny of Endocrine Correlation 



599 



to the state of reactivity of the gonad, being 

 higher in older than in younger stages. Since 

 the structural and functional changes that 

 resvilt from hypophysectomy may be pre- 

 vented or restored to normal by the adminis- 

 tration of gonadotrophins (in the form of 

 either implants or extracts), it is clearly 

 evident that the processes of maturation of 

 the gonad are dependent upon the presence 

 of specific hypophyseal secretions. Such se- 

 cretions are clearly essential to the main- 

 tenance of structural development and func- 

 tion of the gonads, beginning early in post- 

 natal life of the rat and mouse, and even 

 prior to birth in the rabbit, as noted above 

 (p. 595). 



The correlation of the time of onset and 

 subsequent increase of gonadotrophic activity 

 with histogenesis of cell types of the ante- 

 rior pituitary is a difficult problem to re- 

 solve. Only a few studies have been oriented 

 toward its solution. The time course of 

 differentiation of the chromophilic cells as 

 related to the initiation of gonadotrophic 

 activity has been worked out most completely 

 for the anterior lobe of the pig fetus (Smith 

 and Dortzbach, '29; Nelson, '33). The baso- 

 philes differentiate first (50- to 60-mm. stage), 

 then increase markedly in number, and be- 

 come the predominate type between the 70- 

 to 100-mm. stages. The acidophiles arise first 

 at the 70- to 80-mm. stage, gradually in- 

 crease in number during subsequent stages, 

 and at the 160- to 170-mm. stage show a 

 marked rise. This decided increase in number 

 of acidophiles coincides approximately with 

 the time (170- to 1 80-mm. stage) that the 

 gonad-stimulating hormone is first indicated 

 by functional tests. The activity, although 

 slight at first, increases at the 200- to 221-mm. 

 stage and still more at the 250-mm. stage. 

 Since a significant increase in the acidophile 

 population precedes by a short interval of 

 time the initiation of gonadotrophic activity, 

 it would appear that an age relationship 

 exists between acidophile differentiation and 

 the appearance of the gonad-stimulating 

 principle. 



Although such a corresponding relation 

 probably has significance in understanding 

 the ontogeny of functional activity of the 

 hypophysis as an integrated glandular organ, 

 it has little value in assigning a specific 

 physiological secretion to a particular cell 

 type. The shift in proportional numbers of 

 the three kinds of cells and their changes 

 in cell structure under experimental condi- 

 tions comprise a much more reliable indi- 

 cator of the cell strain involved. By disturbing 



experimentally the interfunctional relation 

 of anterior pituitary and gonad (including 

 sex structures dependent upon gonad secre- 

 tions) during embryonic life, significant new 

 clues may be obtained as to the possible 

 relationship of the time order of differentia- 

 tion and relative frequency of the cell types 

 at a given stage with the onset and increase 

 of gonadotrophic activity. Specially indicated 

 is a study of the effects, either separately or 

 in combination, of embryonic castration and 

 the injection of sex hormones, each of which 

 during postnatal (or equivalent) stages is 

 known to alter the anterior pituitary both in 

 structure and in gonadotrophic activity 

 (either acceleration or inhibition). Also, in 

 ascertaining the possible secretory signif- 

 icance of the granules of the chromophiles 

 histochemical methods may be useful. For 

 instance, the periodic acid-Schiff reaction 

 indicates that the granules of the basophiles 

 (adult human pituitary) are mucoprotein in 

 nature (Herlant, '49) and therefore allied 

 chemically to gonadotrophic hormones which 

 contain a proportion of polysaccharides and 

 glucosamine (Evans et al., '39). 



Such studies as are proposed above might 

 equally well be suitable for ascertaining the 

 time in the course of ontogeny that gonad 

 secretions have a reciprocal action on the 

 anterior pituitary. Although the effects of 

 castration, and especially of the injection 

 of sex hormones, on the differentiation of 

 sex structures of the embryo have been 

 widely explored, little or no attention has 

 been directed in such altered physiological 

 conditions to the possible occurrence o^ 

 changes in the anterior lobe. As functional 

 tests indicate, both the gonad and anterior 

 pituitary have hormonal activity beginning 

 at least during the later stages of embryonic 

 life and usually attaining gradually a higher 

 value after birth or an equivalent time. So 

 far as can be judged from the available evi- 

 dence, the interlocking of functional activity 

 is first clearly indicated at about the time 

 the gonads are approaching sexual maturity 

 (Engle, '31). At approximately that time 

 the gonad secretions apparently stimulate the 

 liberation of the gonadotrophic hormones. If 

 correctly determined, does this signify that 

 reciprocal functional relations are established 

 when the gonad attains a level of secretory 

 activity sufficient to cause the release of the 

 previously accumulated gonadotrophins? Or 

 is the relation unidirectional at first, during 

 which time the gonadotrophins are released 

 only in sufficient quantities to maintain 

 gonad growth, maturation, and function? If 



