596 



Ontogeny of Endocrine Correlation 



formation could be stimulated by hypo- 

 physeal implants or injection of gonado- 

 trophins is conjectural. 



Does the production of gonadotrophins in- 

 crease quantitatively with advance in devel- 

 opmental age? As regards the relative 

 gonadotrophic potency at various embryonic 

 ages the available evidence is not easily 

 assessed, inasmuch as different species of 

 animals and different indices of sexual 

 maturity (i.e., precocious ovulation or open- 



elicited in the genital system of the mouse 

 even though the dosage is doubled. Further 

 bio-assay studies are needed at successively 

 later stages in order to ascertain whether 

 the quantity of gonadotrophin continues to 

 increase with fetal age and at what rate of 

 increase. 



After birth a gradual increase in gonado- 

 trophin content is clearly evident. Using, for 

 the bio-assay test, the immature female albino 

 mouse at a stage (20 to 22 days of age; 6 



Fig. 212. The prostatic region of two male rabbit fetuses of the same age (28 days). A, Decapitated at 

 19± days; B, normal litter male control. Note the arrested development of the two anterior prostatic 

 buds in A as contrasted with their ramified stage in B. (Courtesy of Jost, '48.) 



ing of vagina, increase in gonad weight, 

 etc.) were used for the bio-assay test and, 

 moreover, the unit quantity of implants of 

 anterior pituitary tissue either varied greatly 

 or was not considered. Although the data are 

 inadequate for measuring relative potency, 

 they in general do indicate the presence of 

 gonadotrophins in the anterior pituitary of 

 mammals (including the human) at the more 

 advanced stages prior to birth. The most 

 convincing evidence of their quantitative 

 increase during fetal life has come from a 

 study of the pig fetus. Using the immature 

 mouse as the test animal, Smith and Dortz- 

 bach ('29) found that gonad-stimulating 

 hormone is present in readily detectable 

 amounts in anterior pituitaries of pigs of 25 

 cm., in lesser amounts at the 20- to 21 -cm. 

 stage, and none earlier than the 17- to 18-cm. 

 stage. Prior to the last stage no response is 



to 8 days prior to the probable time of onset 

 of sexual maturity in the normal) when the 

 genital system is sensitive to small amounts 

 of anterior pituitary, Clark ('35) determined 

 the amount of gonad-stimulating hormone in 

 the anterior lobe of the rat from the day of 

 birth up to and including sexual maturity. 

 Using increase in ovarian weight as the 

 index of activity, the changes in content 

 with increasing age were determined sepa- 

 rately for each sex. The activity of the female 

 pituitary increases rather gradually during 

 the first week after birth and then rises 

 sharply between the thirteenth and twentieth 

 days (the probable period of most extensive 

 follicular growth in the normal rat), reach- 

 ing at that time a level of activity per unit 

 weight of anterior pituitary which is not 

 excelled at subsequent ages even after full 

 sexual maturity is attained. On the other 



