77?^ Two Components of Semen 3 



the present century, research on semen was, on the whole, confined 

 to fish and generally to animals in which fertilization takes place 

 externally, and which provide the experimental material in con- 

 veniently large quantities. The tardy progress of research on the 

 spermatozoa and seminal plasma of birds and mammals was due 

 in the main to the difficulty of securing enough material for experi- 

 mental purposes; however, more rapid advances were made soon 

 after Elie Ivanov (1907) and several other pioneers in the field of 

 artificial insemination, perfected the technique of semen collection 

 from domestic animals. The widening practice of artificial insemina- 

 tion for breeding purposes on a large scale, early revealed the need 

 for improved standards of sperm evaluation and in this way pro- 

 vided a powerful stimulus for morphological as well as chemical 

 investigations on semen. At the same time, clinical enquiries into the 

 causative and diagnostic aspects of human infertility also pointed 

 to serious gaps and deficiencies in the knowledge of the physiology 

 of human semen. 



The last two decades have witnessed rapid advances in the applica- 

 tion of laboratory methods of semen analysis to the study of the 

 manifold causes underlying male sterility and subfertility, and there 

 is a steadily increasing number of publications on this subject, which 

 has been comprehensively reviewed on several occasions. Some of 

 these articles and monographs refer specifically to man (Joel, 1942; 

 Hammen, 1944; Hotchkiss, 1945; Hinglais and Hinglais, 1947; 

 Farris, 1950; Lane-Roberts, Sharman, Walker, Wiesner and Barton, 

 1948; Bayle and Gouygou, 1953; Longo, 1953; Williams, 1953), while 

 others deal with various animals (Gunn, 1936; Burrows and Quinn, 

 1939; Anderson, 1945; Bonadonna, 1945; Perry, 1945; Walton, 1945; 

 Milovanov and Sokolovskaya, 1947; Van Drimmelen, 1951; Millar 

 and Ras, 1952). In addition, much valuable information on sperm 

 physiology in general, indispensable alike to those engaged in human 

 and in animal research, will be found in the writings of Marshall 

 (1922), Hartman (1939), Chang and Pincus (1951) and Walton (1954), 

 as well as in the published records of various symposia and con- 

 ferences held under the auspices of such bodies as the Biochemical 

 Society {Biochemistry of Fertilization and the Gametes, 1951), the 

 New York Academy of Sciences {Biology of the Testes, 1952), the 

 Ciba Foundation {Mammalian Germ Cells, 1953), the National 

 2 



