FOETAL NUTRITION: THE PLACP^NTA 473 



dilated, and blood extravasations occur between ths cells and 

 into the lumen. The tissue is 

 oedematous and spongy, and 

 the swollen cells often appear 

 to be floating free in a fluid 

 (v. Heukelom). These changes 

 are especially marked near the 

 ovum, and they give rise to 

 an elevation which marks 

 the resting-place of an early 

 blastocyst. The mucosa is 

 differentiated into a superficial 

 layer, the convpacta, and a 

 deeper layer, the sfongiosa, in 

 which are the enlarged middle 

 portions of the glands, arterioles, 

 venules, and lymphatics. In 

 the compacta the connective 

 tissue cells undergo active 

 division, and they enlarge to 

 form the decidual cells (Fig. 

 126). Before the excavation 

 of the " Eikammer " they are 

 probably not found, though 

 Peters described the com- 

 mencement of a decidual 

 change before that stage. In 

 Merttens' ^ ovum large decidual 

 cells were found, many of them 

 fusiform and lying parallel to 

 the surface. The decidual 

 change arises first in the 

 connective tissue cells near 

 the ovum, and later it ex- 

 tends more deeply in the 

 compacta. There is no special 



7?«/. 



Fig. 126.— Condition of the glands 

 at the beginning of pregnancy in 

 Man (after Kundrat and Engel- 

 mann). (From Quain's Anatomy, 

 Longmans.) 



c, compact layer near free surface of 

 decidua: the glands are here some- 

 what enlarged, but not very tor- 

 tuous, and the mucous membrane 

 is rendered compact by the hyper- 

 trophy of the interglandular tissue; 

 sp., spongy layer containing the 

 middle portion of theglandsgreatly 

 enlarged and tortuous, producing 

 it spongy condition in the mucous 

 membrane ; d, deepest portion of 

 glands, elongated andlortuous.but 

 not much enlarged ; m., muscularis. 



perivascular development as 



' Merttens, " Beitrage zur normalen und pathologischen Anatomie der 

 menschlichen Placenta," Zeitschr. f. Geburtsh.u. Gynak., vols, xxx.andxxxi., 

 1894-5. 



