Margaret K. Deringer, Ph.D. 



APPENDIX VI 



Technique for the Transfer of Fertilized Ova 



In studies of mammary tumors in mice, it is often desirable to have animals from 

 which the milk agent is absent but that are susceptible to its action. One of the 

 methods by which such animals are produced, mentioned by Dr. Heston, is the transfer 

 of fertilized ova from a strain carrying the agent to one lacking it. A brief description 

 of the technique of transferring ova, as employed in our laboratory, follows. 



Females of donor and recipient strains, to be employed in the transfer, are mated 

 to their brothers. Each female is allowed to produce and rear one litter before a 

 transfer is attempted. After the litter is weaned the females are returned to the breeding 

 cages and are observed each morning thereafter for the presence of a vaginal plug, 

 an indication that mating has occurred. At selected periods after observation of the 

 vaginal plug, the donor female is killed. If the transfer is made at 52 hours, the ova 

 will be found in the oviducts. The oviducts are removed and put in a watch glass 

 containing filtered physiologic saline at 37° C. They are minced with fine scissors 

 allowing the ova to fall to the bottom of the watch glass where they can be observed 

 under a dissecting microscope. If the transfer is made at 76 hours, the ova are usually 

 in the anterior ends of the uterine horns. The uterine horns and the vagina are removed 

 and put into saline in a watch glass. After the ova are flushed out of the horns by 

 forcing saline through the horns by means of a hypodermic syringe inserted into the 

 vagina, they are recovered with a finely drawn, glass pipette and are transferred in 

 depression slides through several changes of saline. 



The pregnant recipient females, at a period postplug similar to the donor females, 



563 



