CHAPTER V 



METHODS EMPLOYED IN THE EXPERIMENTAL 

 MANIPULATION OF MAMMALIAN OVA 



The first investigators of living tubal eggs (Barry, Cruik- 

 shank, Bischoff, Spee, et al.) used rather laborious methods 

 of dissecting the tubes (see Squier, 1932, for an interesting 

 historical discussion). The modern technique of securing 

 eggs from the fallopian tubes of most mammals is a fairly 

 simple one. Nonetheless, certain surprising differences in 

 the behavior of the obtained ova arise when exactly the 

 same methods are applied to two different species. Among 

 the laboratory mammals the rabbit is by far superior, and 

 for one very simple reason, namely, rabbit ova seem to 

 withstand the process of handling better than other ova. 

 Mouse, rat and guinea pig ova, for example, begin to frag- 

 ment very soon after removal from the tubes (Lewis, 1931; 

 Gilchrist and Pincus, 1932; Squier, 1932; and Defrise, 1933) 

 and to date it has been possible to observe at most one or 

 two cleavages in culture, whereas rabbit ova will go through 

 the whole course of cleavage and blastulation in vitro. 



The long, fairly straight tubes of most mammals can 

 easily be washed through by a Ringer-Locke or similar bal- 

 anced salt solution. The writer has found that a Ringer- 

 Locke solution to which has been added an equal amount 

 of homologous blood serum is most useful. It is necessary 

 only to free the tubes of their mesenteric connections, and 

 if the tubes only are to be employed to cut them away from 

 the uterus. It is ordinarily best to cut off the uterus at 

 about one-half inch from the ampulla so that if washing 

 backward toward the fimbria is desired a certain length of 

 uterine lumen will be available for the guidance of the 

 washing pipette. When ova are to be washed downward 



62 



