Maternal Part of the Placenta. 



103 



blood vessels show an interesting change. At a very early period 

 the endothelial lining becomes transformed into syncytial and 

 plasmodial masses. It was of interest to determine whether the 

 deciduae produced experimentally in the guinea-pig and in the 

 rabbit differed in the same way as the normal deciduse in these two 

 species. 



The following experiments were, therefore, carried out : 



1 . In four female rabbits which had been kept separated from 

 males for some time previous to the operation and which were not 

 pregnant, no deciduomata were formed after the usual incisions 

 into the uterus had been made. We found only edematous mucosa 

 on microscopic examination. 



2. Three rabbits were operated, 3 to 5 days after copulation. In 

 two of these animals the nodules, formed ten days after the opera- 

 tion, were examined microscopically. They showed the above 

 mentioned characters of the maternal part of the placenta of the 

 rabbit. 



3. These latter experiments were, perhaps, open to the objec- 

 tion that ova had come into contact with that part of the mucosa 

 which gave rise to the formation of decidual tissue. Although 

 such an occurrence was extremely unlikely inasmuch as the con- 

 tinuity of the uterine cavity had been interrupted, through the 

 operation, at many places, two other experiments were performed, 

 in which, in each case, both fallopian tubes were tied at their 

 junction with the uterine horns about 1 ^ hours after copulation. 

 Seven days later the ordinary incisions were made into the uterus. 

 Ten days later many decidual nodules were formed in both cases, 

 which, on microscopic examination, showed the characteristic fea- 

 tures of the rabbit placenta, namely, the vacuolated cells, the plas- 

 modial changes of the blood vessels, and besides, the formation 

 of multinucleated cells in the uterine epithelial layer, which repre- 

 sented the first step in the formation of epithelial plasmodia. 



These changes, however, did not occur at every point simulta- 

 neously. The plasmodial transformation of the blood vessels was 

 sometimes seen without the accompanying formation of vacuolar 

 cells ; at other places both changes were present in the same area. 

 On the whole, the nodules in the rabbit were, in proportion to the 

 size of the rabbit uterus, considerably smaller than the deciduo- 

 mata formed in the guinea-pig. 



