AL 





ROLE OF HORMONES IN THE 

 DIFFERENTIATION OF SEX 



R. K. Burns, Ph.D., D.Sc. ihon.) 



CA.RNEGIE INSTITUTION OF WASHINGTON, DEPARTMENT OF EMBRYOLOGY, 

 THE JOHNS HOPKINS UNIVERSITY, BALTIMORE, MARY'LAND 



I. The Hormone Theory of Sex Dif- 

 ferentiation 76 



II. Methods of Experimental Analy- 

 sis 78 



A. Grafting of Gonads or Gonad Tis- 



sues in Bird Embryos 78 



B. Grafting Experiments in Amphib- 



ian Embrj'os 79 



C. Use of Pure Hormones as Sex Dif- 



ferentiating Agents 82 



D. Sex Differentiation in the Absence 



of Hormones 82 



III. The Bisexual Organization of the 



IiIarly Embryo as the Basis of Sex 

 Reversal 83 



IV. Experimental Reversal of Sex Dif- 



ferentiation IN the Gonads 83 



A. Bisexual Organization of the Gonad 



and the Physiologic Mechanism 



of Sex Differentiation 83 



B. Sex Reversal in Amphibian Gonads 86 



1. Constitutional differences and 



the character of the reversal 

 process 80 



2. Parabiosis and grafting of the 



gonad or the gonad primordium 87 



3. Administration of steroid hor- 



mones 91 



C. Sex Rkv'ersal in Avian (Ionads. 95 



1. Organization of avian gonads. . . 95 



2. Effects of administering pure 



hormones 9(i 



3. Effects of grafting gonads into 



the coelomic cavity 99 



4. Sex reversal in vitro 100 



D. The Problem of Sex Reversal in 



Mammalian Gonads 100 



1. Bisexual potentialities in the 



embryonic gonads of mammals 100 



2. Bisexual potentiality in the em- 



bryonic ovary of the rat 103 



3. Experimental transformation 



of the testis in the opossum. . . 105 

 V. The Role of Hormones in the De- 

 velopment OF the Accessory Sex 

 Structures 110 



A. Differentiation of the Embryonic 



Gonaducts Ill 



1. The Miillerian ducts 112 



2. The male duct system 120 



B. Derivatives of the Cloaca and 



Urinogenital Sinus 121 



C. External Genital Structures 127 



D. Differentiation of Other Types of 



Sex Character 129 



VI. The Pituitary and the Differen- 

 tiation OF Sex 132 



VII. Group Differences in the Rela- 

 tions OF Hormones to Sex 134 



VIII. The Organization of the Sex Pri- 

 mordium AND Its Role in the Dif- 

 ferentiation OF Sex 137 



A. Constitution and the Morphologic 



Representation of Sex Primordia 137 



B. Constitutional Factors and Physi- 



ologic Differences in the Organi- 

 zation of Sex Primordia 138 



C. Influence of Sex Genotype on the 



Reactions of Sex Primordia 139 



IX. The Time F'.^ctor in the Responses 

 OF Sex Primordia: Receptivity 



and "Critical Periods" 140 



X. Specificity of Hormone Action and 

 the Significance of P.\radoxical 



Effects 141 



XI. Time of Origin and the Source of 



(ioNAD HoR.MONES 143 



XII. A Comparison of the Effects of Em- 

 BRYt)Nic and Adult Hormones in 

 Skx Differentiation 145 



.\1I1. IvMBRYONic Hormones and Inductor 



Substances 148 



XIV. References 151 



I. The Hormone Theory of 

 Sex Diflfereiitiation 



The modern era in the study of the pliys- 

 iology of sex differentiation is iisually dated 

 from the sohition of the freemartin iiroblem 

 through the simultaneous but entirely inde- 



76 



