104 Scientific Proceedings (57). 



merits I had shown that in the guinea pig only the mucosa of the 

 uterus is able to produce a decidua under the influence of experi- 

 mentally applied stimuli. In the human organism where extrau- 

 terine pregnancy occurs, decidua can to some extent form also at 

 certain places outside of the uterine mucosa. It is, therefore, 

 probable that one of the factors upon which the development of 

 an extrauterine pregnancy depends is the capability of the tissue, 

 into which the ovum penetrates, to develop decidual tissue which 

 presents to the ovum an adequate soil for development. 



In an experiment carried out recently I was able to show that 

 it is possible to produce experimentally the first stages of an 

 extrauterine pregnancy in the guinea pig, that however the de- 

 velopment of embryo and placenta outside the uterus ends 

 prematurely. 



Incisions were made into the uterus of a guinea pig two days, 

 sixteen hours after copulation. The incision reached upwards 

 through the greater part of both horns. Eighteen days after 

 copulation, examination of ovary and uterus showed that a new 

 ovulation had taken place approximately three days previously, 

 fifteen days after the preceding copulation. On the peritoneal 

 side of the left horn of the uterus, near the fallopian tube was 

 embedded superficially in the tissue a young embryo in which 

 structures appear which resemble the neural canal, coelomic and 

 enteric cavities and the anlage of the blood vessels. These struc- 

 tures are somewhat distorted. They are surrounded by placental 

 formations, namely, syncytia, plasmodia and small cuboidal cells. 

 The giant cells penetrate into the surrounding tissue of the uterine 

 peritoneal coat and ensheath especially the blood vessels, substi- 

 tuting their wall; the small cuboidal cells supply the lining of 

 cavities, into the interior of which they send papillary processes. 

 Frequent mitoses are present in the cuboidal cells; occasionally 

 a mitosis can also be seen in a giant cell. The plasmodia sur- 

 round externally these coats of cuboidal cells. Some hemorrhages 

 surround the whole structure and a little connective tissue of the 

 peritoneal coat of the uterus covers it. Decidual tissue is entirely 

 absent. There is no reaction on the part of the surrounding host 

 connective tissue or of the blood vessels. We have without doubt 

 to deal with an ovum which escaped from the upper end of the 



