FOREWORD 



George W. Corner, M.D., D.Sc. 



DIRECTOR EMERITUS, DEPARTMENT OF EMBRYOLOGY, 

 CARNEGIE INSTITUTION OF WASHINGTON 



Publication of the third edition of Sex 

 and Internal Secretions signalizes the ac- 

 complishment of about a half century's 

 intensive work by investigators of many 

 countries, among whom those of the United 

 States have been notably active. Any such 

 burst of discovery as this rests, of course, 

 upon a long preceding period of more 

 gradual progress. Taking as landmarks Reg- 

 ner de Graaf's recognition that the "female 

 testis" of mammals is an egg-producing 

 organ comparable to the ovaries of birds 

 (1672) and Leeuwenhoek's description of 

 the spermatozoa (1674), we can trace the 

 continuous development of knowledge about 

 the reproductive system down to our own 

 times. Discovery of the actual mammalian 

 ovum by Karl Ernst von Baer in 1827 

 accelerated the progress of research on the 

 origin of the germ cells, the de^'elopment and 

 discharge of the Graafian follicle, transport 

 and fertilization of the ovum, and implanta- 

 tion and development of the embryo. Such 

 studies inevitably drew attention to the 

 cyclic aspects of reproductive function, par- 

 ticularly from students of animal breeding 

 and from faunal naturalists, who acquired a 

 great deal of information about the estrous 

 cycles of wild as well as domestic animals 

 and those of the laboratory. The work 

 of the English leaders in this kind of in- 

 vestigation, Walter Heape and F. H. A. 

 Marshall, reached fruition in the latter's 

 well known "Physiology of Reproduction," 

 published in 1910. At this same period 

 (1890-1910) gynecologists, especially in Ger- 

 many and Austria, were putting their spe- 

 cialty on a scientific basis. Becoming aware 

 of the current advances in knowledge of 

 embryology and the biology of reproduction 

 of mammals in general, they were seeking 

 similar clues to the explanation of the 

 human menstrual cycle, ostensibly so dif- 

 ferent from the estrous cycle of domestic 

 animals. European workers, notably Hitsch- 



mann and Adler, Robert Schroedcr, and 

 Robert Meyer, from about 1900 to the 

 beginning of the first World War, put to- 

 gether from operating-room material a histo- 

 logic description of the human cycle that 

 became more and more clear as the em- 

 bryologists related it to their understanding 

 of the general mammalian cycle. The young 

 sciences of psychology, psychiatry and an- 

 thropology also joined the concerted attack 

 upon the problems of sex and reproduction. 

 Since about 1870 European psychiatrists, led 

 by such men as von Krafft-Ebing and Forel, 

 had been studying sex psychology, with 

 the aim of understanding behavior of a 

 kind that was considered abnormal or con- 

 ducive to social difficulties such as those 

 created by prostitution and homosexuality. 

 The way was thus opened for psychology 

 to investigate the biologic basis of normal 

 sex behavior. European and American an- 

 thropologists had begun to document and 

 analyze the sex attitudes of primitive races 

 and distant nations, and even of their own 

 peoples. Nor must we forget the influence 

 of the Women's Rights movement, with its 

 fight against all forms of bondage of women 

 and its emphasis on standards of sex be- 

 havior equally applicable to both sexes. 

 All these new sciences and new social move- 

 ments called for better understanding of 

 basic sex physiology, which only biologists 

 could provide. 



Thus at the beginning of the 20th century 

 and during the next decades investigation 

 in this field became more intense. Na- 

 turalists, animal breeders, histologists, em- 

 bryologists and gynecologists gradually came 

 to understand each other's problems, and 

 began a period of rapid advance not yet 

 ended nor even slowed down, in which 

 scarcely a year has passed without major 

 contributions. 



American zoologists were already prepared 

 by their embryologic studies to take part 



