Fig 



7-day 



3 (Russell). Implant of placental end ot divided 

 (CBAx A) Fj hybrid conccptus (the ectoplacental cone) beneath 

 kidney capsule of CBA recipient which had twice rejected A-strain 

 skin grafts. This specimen, removed lo days after implantation, 

 shows vigorous proliferation of trophoblastic giant cells with 

 virtually no attendant host reaction. (Haematoxylin and 

 eosin. x 70.) 



^ %^ 





:,Y«. 



p, i 







Fig. 4 (Russell). Growth of (CBAx A) 



F^ trophoblast beneath 



kidney capsule of CBA recipient which had twice rejected A-strain 

 skin grafts. This has occurred in the 11 days since the original 

 implant, a fertilized ovum of 8 cells. Virtually no host cellular 

 reaction has been provoked in spite of the intimate contact 

 between these tissues. (Haematoxylin and eosin. x 42.) 



