HORMONES IN DIFFERENTIATION OF SEX 



149 



versing gonads occur at the same time and 

 are of the same histologic character as those 

 attributed to inductor action. Evidently the 

 effects of gonads acting from a distance 

 through the agency of blood-borne hor- 

 mones are not distinguishable from those 

 attributed to inductor substances when the 

 interacting gonads are in close juxtaposi- 

 tion. 



Furthermore, in other experimental situ- 

 ations where hormones are almost certainly 

 involved, effects of a strongly localized 

 character can be observed under proper 

 conditions. When sexually differentiated 

 gonads are grafted into the coelomic cavity 

 of chick embryos (Wolff, 1946) ovaries have 

 a transforming effect on the testes of male 

 hosts which varies according to their rela- 

 tive proximity; and at the same stage of 

 development testis grafts modify the adja- 

 cent gonaducts. A similar response appears 

 when well differentiated larval gonads of 

 Amhystoma are transplanted into the body 

 cavity of another larva (Fig. 2.3) and in 

 this case the effects are reciprocal. Also, 

 after unilateral castration of male rabbit 

 embryos (Jost, 1953), the sex accessories on 

 the two sides of the body may show distinct 

 differences in reaction. On the unoperated 

 side normal differentiation of the sex ducts 

 occurs, but on the operated side the Miil- 

 lerian ducts are not completely inhibited 

 and the Wolffian ducts are only partially 

 preserved (c/. also Price and Pannabecker, 

 1956). It would seem that the remaining 

 testis produces enough hormone to insure 

 normal development of nearby structures, 

 but at this early stage its output is insuffi- 

 cient to maintain proper development of 

 structures at greater distances. A compara- 

 ble result was obtained when an embryonic 

 testis was implanted in a female embryo in 

 close proximity to one ovary of the host 

 (Jost, 1947b, 19531. The ovary on the side 

 of the grafted testis was inhibited and 

 atrophic whereas the other was normal (Fig. 

 2.35), and duct development followed dif- 

 ferent patterns on the two sides. On the 

 side of the testis graft the Wolffian duct and 

 epididymis persisted and developed but the 

 IMiillerian duct was suppressed in the vi- 

 cinity of the graft. On the side of the nor- 

 mal ovary these relationships were reversed. 



Evidently the pattern of development is de- 

 termined by proximity to the grafted testis. 

 The same situation as regards the differ- 

 entiation of the sex ducts and accessory 

 structures is often encountered in so-called 

 "lateral gynandromorphs" which occur spo- 

 radically in many mammals. In such cases, 

 where embryonic hormones are clearly in- 

 volved, the localized aspect of their action 

 often resembles closely the postulated ef- 

 fects of inductor substances. It is interesting 

 to compare the results of the experiments 

 cited above with conditions found in a type 

 of lateral gynandromorphism of doubtful 

 etiology which occurs in a certain genetic 

 strain of mice (Hollander, Gowen and Stad- 

 ler, 1956). These gynandromorphs have an 

 ovary on one side and a testis on the other, 

 but without relation to laterality. Typically 

 both gonads are small and underdeveloped, 

 with the testes as a rule more severely af- 

 fected. It is the condition of the accessory 

 sex structures in these cases that is of spe- 

 cial interest. On the side of the testis, de- 

 velopment of the gonaducts without excep- 

 tion follows the male pattern (24 cases), a 

 vas deferens and epididymis are present, 

 and Miillerian duct derivatives are lacking 

 (Fig. 2.36). This condition corresponds ex- 

 actly to the role of the testis as the condi- 

 tioner of male duct development and the in- 

 hibitor of the Miillerian duct, as revealed by 

 the results of castration and culture in vitro. 

 The development of the seminal vesicles is 

 variable and the external genitalia, although 

 usually underdeveloped, are nearly always 

 of male type. These conditions in turn can 

 be correlated with the size of the testis and 

 the factor of distance from a gonad which 

 is probably subnormal in its secretory ac- 

 tivity. On the side of the ovary the oppo- 

 site picture prevails; the Miillerian deriva- 

 tives are always present, although variable 

 in size, whereas the male accessories are 

 either imperfectly developed or in most 

 cases altogether lacking. A similar condi- 

 tion has recently been reported in a gy- 

 nandromorphic hamster (Kirkman, 1958) . It 

 may be noted that lateral differences of this 

 kind are not infrequently met with in cer- 

 tain human intersexes (Jost, 1958; Wilkins, 

 1950). 

 Evidence from other types of experiment 



