The Two Components of Semen 9 



Whether the semen is ejaculated into the uterus (sow), or into the 

 cervix or vagina (cow, rabbit), a certain time is always required for 

 the passage of spermatozoa to the oviducts and for their accumula- 

 tion in adequate numbers at the site of fertilization. The time needed 

 for some of the spermatozoa at any rate, to arrive at their goal may 

 be relatively short; a quarter of an hour or less, in the rat (Blandau 

 and Money, 1944), cow (VanDemark and Moeller, 1951) and ewe 

 (Starke, 1949; Dauzier and Wintenberger, 1952); a matter of a few 

 minutes in the rabbit (Lutwak-Mann, unpublished). This indicates 

 that in these animals the spermatozoa are conveyed to their final 

 destination thanks to certain concomitant movements of the 

 female tract and do not depend exclusively upon their own motility. 

 However, from the moment of arrival in the ovarian tube, time 

 must elapse before the sperm cell is capable of fertilizing the egg. 

 In the rabbit, ovulation takes place about ten hours after copulation, 

 and presumably, spermatozoa require this period of time to undergo 

 complete 'capacitation'. As Chang (1951) has shown, rabbit sperma- 

 tozoa placed in the Fallopian tubes soon after ovulation, penetrate 

 a larger proportion of eggs if they had been previously kept for about 

 five hours in the uterus of another doe. According to Austin (1951), 

 rat spermatozoa injected into the periovarian sac of the rat after 

 ovulation, do not begin to enter the eggs until some five hours later. 

 The processes of sperm maturation and capacitation are linked in 

 some as yet not fully understood manner, with the survival of sperm 

 in the female tract. In higher mammals this period is usually limited 

 to one or two days, but the 'longevity' of bird sperm is remarkable, 

 and in bats and the terrestrial isopode Armadillidium vulgare the 

 spermatozoa are said to survive in the female tract for many months, 

 in certain insects even for years. In insects, however, this striking 

 behaviour of spermatozoa is probably bound up closely with certain 

 other peculiarities of sperm transport: in many instances, the sperma- 

 tozoa are conveyed to the female not in a free fluid medium, but are 

 enclosed in a sac or 'spermatophore' which is deposited in the 'bursa 

 copulatrix' or in the vagina; from there, after the sac has been 

 emptied, they move on to the 'spermatheca', a pouch which serves 

 as a special storage organ for the spermatozoa, where they remain 

 till the time of fertilization. 



It must also be remembered that not all spermatozoa present in 



