112 MAMMALIAN FERTILIZATION 



hours after mating. After the pubHcations by Chang (1951b), 

 Moricard (1954), and Dauzier et at (1954), attempts were made 

 to fertihze rabbit eggs in vitro by uterine or tubal sperm under 

 anaerobic or aerobic conditions, and in the presence or absence 

 of the Fallopian tube. Unfortunately no fertilization was observed 

 (Chang, unpublished). Dr. C. R. Austin told the writer on De- 

 cember 1, 1955, that he was unable to fertilize eggs in vitro with 

 uterine or tubal sperm. It seems that there are still other factors 

 involved beside the "capacitation" of spermatozoa in the female 

 tract. 



From the above account, it seems that up till now we still do 

 not have a repeatable procedure to fertilize mammalian eggs in 

 vitro. This is not necessarily due to the requirement of an anaer- 

 obic condition because the Fallopian tubes are very vascular 

 ( Plate 1,1). Neither can it be due to temperature change or eggs 

 being rendered unfertilizable once removed from the tube, be- 

 cause freshly shed rabbit eggs can be stored at 10° or 0° C. for 

 1 day without losing their fertilizability when transferred into 

 the tubes of mated animals (Chang, 1953). Although the physi- 

 cal and chemical environment of the Fallopian tube is important 

 for fertilization, it is not the only place that fertilization can take 

 place because freshly shed rabbit eggs can be fertilized when 

 transferred into the uterus of mated rabbits, but degeneration 

 occurs quickly ( Chang, 1955c ) . It seems that the motility of the 

 Fallopian tube and unknown enzyme systems present in the tube 

 which interact with sperm and eggs may play a role in mamma- 

 lian fertilization. 



Lillie (1923) stated that "the conditions to be fulfilled in fer- 

 tilization involve, not only penetration of the spermatozoon, or 

 some part of it, into the egg but also reaction between the two." 

 He therefore speaks of "a fertilization reaction when the behav- 

 ior of both partners indicates that the process is proceeding nor- 

 mally." In this respect, the fertilization reaction in the mammalian 

 species may involve a third partner, that is, the Fallopian tube. 

 Parkes ( 1951 ) mentioned that "the biochemical changes involved 

 in penetration, activation and syngamy are almost completely un- 

 known in mammals, and are likely to remain so until fertilization 



