EXPERIMENTALLY PRODUCED EXTRAUTERINE PREGNANCY. 75 



to the transformation of blastomeres or of remnants of not fully 

 differentiated embryonal tissues into teratomata, an hypothesis 

 which would be in accordance with the finding of misplaced 

 blastomeres by W. Roux in the course of the embryonal develop- 

 ment of amphibian eggs. 



Summary. 



1. It is possible in the case of guinea pigs to produce experi- 

 mentally the first stages of an extrauterine pregnancy. 



2. In a similar manner, as in the case of guinea pigs experi- 

 mental interferences of various kinds are not able to call forth 

 the production of deciduomata in the connective tissue outside 

 of the uterine mucosa after the discharge into the circulation of 

 the sensitizing substance which is secreted by the corpus luteum, 

 the developing ovum is unable to call forth a decidual reaction. 



3. Under the conditions produced by us experimentally the 

 development of the embryo is very much retarded and will in all 

 probability come to a standstill after some time. Neither does 

 the embryonal placenta develop in an entirely normal manner, 

 although quantitatively the embryonal placental structures 

 preponderate considerably over the embryonal proper. It is very 

 probable that the lack of the decidual and of the typical blood 

 vessel reaction on the part of the host connective tissue is the 

 cause of this abnormal development. In man an extrauterine 

 decidua can develop and accordingly here a fully developed 

 extrauterine pregnancy is not rare. As we have shown pre- 

 viously the effect of the extirpation of the corpora lutea on the 

 formation of the decidua and on the development of pregnancy 

 is approximately parallel. This is an additional fact which 

 renders probable the significance of the decidual reaction for the 

 complete development of the extrauterine pregnancy. The 

 decidual reaction is at least one of the conditions which has to 

 be considered in this connection. 



4. Notwithstanding the presence of a young, developing em- 

 bryo in the extrauterine connective tissue a degeneration of the 

 corpora lutea and a new ovulation took place in the ovary. This 

 proves that the persistence of the corpora lutea during pregnancy 

 does not depend upon a substance secreted by the embryo; it is 



