Fate of Embryonic Tissue Implanted in Mother. 71 



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The fate of embryonic tissue implanted in the mother. 



By PEYTON ROUS. 



[From the Laboratories of the Rockefeller Institute for Medical 

 Research, New York.~\ 



The following experiments were done primarily to ascertain 

 whether there exists, specific to the pregnant animal, a substance 

 favoring the growth of embryonic tissue. 



Many pregnant white mice were hysterectomized (leaving the 

 ovaries in situ), and a measured portion of the hashed embryo 

 implanted through a needle subcutaneously. The animals showed 

 themselves only slightly susceptible to infection at operation, and 

 in the great majority the laparotomy wound healed promptly and 

 the general health remained good. It was found that the embry- 

 onic tissue grows profusely when implanted in the mother, yet not 

 better than in certain unoperated, alien hosts. No evidence of a 

 favoring substance specific to the pregnant animal was obtained. 



In a number of experiments two mice were hysterectomized, 

 and separate grafts of the hashed embryo from each were made in 

 both, using the subcutaneous tissue of the flanks as the site of im- 

 plantation. In general the embryonic material grew better in the 

 animal that had furnished it, — a new demonstration of the im- 

 portance of blood-relationship in transplantation. 



It proved feasible to snare off from the forked uterus of the 

 mouse one or more embryos, without damage to the others, which 

 go on to term. The implanted material fails to grow in these 

 mothers that still carry young. The contrast to what occurs in 

 the completely hysterectomized mother, or in a favorable alien 

 host, or, for that matter, in an unfavorable alien host is very 

 striking. 



As I have shown elsewhere, 1 individual mice differ much as 

 hosts for the same hash of mouse-embryo. In some it is promptly 

 vascularized and grows well, whereas in others no vascularization 

 occurs and the fragments die within a few days. Histological 

 examination shows that embryo implanted into the mother is 



^ four, of Exper. Med., 1910, XII, No. 3. 



