C. R. AUSTIN AND M. W. H. BISHOP 83 



owing in part to the protective action of nonelectrolytes. There 

 is evidence, too, of a specific protective agent. Lindahl and his 

 associates claim to have isolated a highly potent antagglutin 

 from the semen of several mammals and to have demonstrated 

 its presence also in the secretions of the vagina, cervix, and Fal- 

 lopian tubes and in the ovarian follicle (Lindahl and Kihlstrom, 

 1954a,b; Lindahl and Nilsson, 1954; Furuhjehn, Nilsson, Lindahl, 

 and Ingleman-Sundberg, 1954; Lindahl and Edkmd, 1955). The 

 antagglutin appears to be a mucoprotein; it is nondialyzable and 

 can be reversibly oxidized. It is evidently produced in the prostate 

 gland and becomes attached, while in the reduced form, to the 

 spermatozoa thus preventing head agglutination, in which func- 

 tion it exhibits no species specificity. On oxidation, the ant- 

 agglutin is inactivated and is detached from the spermatozoa, 

 whereupon head agglutination takes place. The active agent is 

 apparently stabilized in semen by the presence of reducing sub- 

 stances such as ergothionine and ascorbic acid. Such an antag- 

 glutin would have an important function in the seminal plasma 

 and throughout the female genital tract in maintaining the sper- 

 matozoa in a suitable state for reaching and penetrating the eggs. 



A protective action of vaginal mucus in the rabbit against the 

 specific tail agglutination induced by appropriate antisera has 

 been demonstrated by Smith ( 1949a ) . 



Maintenance in the female tract therefore involves both sup- 

 ply of metabolites to spermatozoa and protection against the ad- 

 verse effects of the inevitable high dilution that spermatozoa 

 undergo. 



Capacitation 



An important function of the female genital tract is the part it 

 plays in the process of capacitation, whereby the spermatozoon 

 gains the ability to pass through the zona pellucida and thus to 

 enter the egg ( see Austin, 1955b ) . That spermatozoa are required 

 to spend a period of a few hours in the female tract before they 

 are able to penetrate eggs was shown by introducing suspensions 

 of spermatozoa into the periovarian sac of the rat or into the Fal- 

 lopian tube of the rabbit shortly after ovulation (Austin, 1951; 



