I70 THE PHYSIOLOGY OF REPRODUCTION 



about 226,000,000 spermatozoa, but that the number may vary from 

 zero to 551,000,000. 



Lloyd-Jones and Hays ^ have investigated the effects of excessive 

 sexual activity upon the semen and offspring of rabbits. They found 

 that the semen becomes less viscous and the spermatozoa less 

 numerous while their motility is somewhat reduced also. The 

 percentage of pregnancies induced by the services becomes less as 

 the number of previous services increases, but the sizes of litters 

 actually born do not appear to be reduced until after the fifteenth 

 copulation. The offspring themselves were not affected, except 

 possibly in regard to sex (see below, Chapter XIV,, p. 63-7). 



The spermatozoa which are not ejaculated degenerate. The tails 

 break off, and undergo a gradual liquefaction. The end products are 

 ultimately absorbed by the epithelial cells of the seminal vesicles, 

 and perhaps by the cells of the vasa deferentia or of the testis itself. 

 According to Perez,^ the spermatozoa of male newts which are kept 

 apart from females are absorbed by phagocytes.^ 



Movements of Spermatozoa 



When the. spermatozoa are in the testis they are inactive, but 

 they begin to move rapidly as soon as they are ejected in the seminal 

 fluid. The rate at which they progress has been estimated at 3'6 

 millimetres per minute.* Bischoff* found spermatozoa at the top 

 of the oviduct in the rabbit nine or ten hours after coition. 



It is probable that the ejected spermatozoa continue to undergo 

 movement, as a general rule, so long as they retain their vitality, the 

 rate of movement becoming gradually diminished and ceasing 

 altogether shortly before death. In bats, however, during the 

 period of hibernation the sperms become quiescent without dying, 

 their vigour being restored in the spring when they conjugate with 

 the ova.^ It is exceedingly probable also that in the spotted 

 viviparous salamander and the other animals referred to below 



' Lloyd-Jones and Hays, "The Influence of Excessive Sexual Activity of 

 Male Rabbits," I. and II., Jonr. of Exp. Zool., vol. xxv., 19X8. Cf. Amantea, 

 "Eecherches sur la S6cr6tion Spermatique," Arch. Ital. de Biol., -vols. Ixii. to 

 Ixiv., 1914-16. 



2 Perez, " E6sorption phagocy taire des Spermatozoides," Prooes-Verhaux de 

 la Soc. des Sciences de Bordeaux, 1904. 



3 For chemistry of the spermatozoon and semen, see Chapter VIII. 



* Lott, Anatomie und Phyaiologie des Cervix Uteri, Erlangen, 1871. According 

 to Adolphi ("Ueber das Verhalten von Schluhgenspermien in stromender 

 Fluasigkeiten," Anat. Am., vol. xxix., 1906), the spermatozoa of the adder swim 

 at the rate of 50 m to 80 m per second. 



^ Bischoff, Die Entwichelung des Eaninchen-Eies, Giessen, 1842. 



8 See p. 131. 



