THE PLACBNTATION OF PEEAMELES. 421 



alterations as iu the placental region. Here^ however, the 

 vessels are not nearly so numerous as in the latter. 



Allantoic Placental Syncytium. — Following the folds 

 of the mucosa in section, this portion of the syncytium has a 

 breadth of about 9 mm. in the mid region of the placental 

 area; it varies in thickness from '15 to '28 mm., and is thus 

 slightly thicker on the average than in Stage D. 



The syncytium here is now in active process of absorption 

 and retrogressive metamorphosis. 



The syncytial protoplasm is coarsely granular, and numerous 

 irregular spaces and clefts occur throughout its extent (figs. 

 27 and 28, sp.). Its nuclei are much less numerous, and no 

 longer form such distinct nest-like groups in the syncytial 

 lobules (fig. 29). They vary very greatly in size and in shape, 

 being often quite irregular, and occur in all stages of retro- 

 gressive change. Many of them are vacuolated and greatly 

 hypertrophied (fig. 27). 



Throughout the protoplasm great numbers of leucocytes 

 occur. The majority of these are of the polynuclear variety, 

 possessing oval or rounded slightly staining cell bodies, in which 

 numbers of small deeply staining nuclei lie (fig. 27, p. hue). 



It seems certain that these polynuclear leucocytes are the 

 active agents in the absorption and removal of the degenerat- 

 ing syncytium, and accordingly it may be observed that the 

 leucocytes greatly predominate in the more degenerate areas. 



The placental syncytium is still vascular (figs. 28 and 29), 

 though the superficial capillaries are now not nearly so pro- 

 minent as in Stage D. 



The persistence even in this advanced stage, of compara- 

 tively unaltered portions of the syncytium, shows that no 

 essential alteration takes place in the latter from Stage D up 

 to the time of birth, and that the features peculiar to the 

 present stage are solely characteristic of post-partum meta- 

 morphosis. 



Syncytium beyond Allantoic Placental Area. — This 

 portion of the syncytium has undergone more marked altera- 

 tion in character than the placental portion. On its deeper 



