460 THE PHYSIOLOGY OF REPRODUCTION 



in the mucosa. The sub-epithelial connective tissue cells pro- 

 liferate and form a distinct compact zone. All the capillaries 

 dilate, even before the disappearance of the zona pellucida, and 

 give off many new branches. The tissue fluids are increased, 

 and a serous fluid is transuded and forms, with the glandular 

 secretion, a coagulum around the ovum (Van der Stricht ^). 



On the mesometrial side, the trophoblast thickens around 

 the formative cell mass, and absorbs the surface epithelium. 

 At the opposite pole the cells are flattened, and they also dis- 

 appear. The ftetal ectoderm, which thus comes in contact 

 with the connective tissue, is composed of two layers at the 

 embryonic pole, the flasmodihlast, and, internally to it, the 

 cytoblast. At the non-embryonic or anti-mesometrial pole 

 the plasmodiblast is absent. 



The decidua also differs at the two poles. Opposite the 

 non-embryonic pole, the ceUs remain epithehoid and undergo 

 Uttle change. Where they come in contact with the tropho- 

 blast, they show a tendency to necrose. At the placental pole 

 the deeper layers are also composed of epithelioid cells, but 

 superficially the capillaries continue to dilate and make the 

 layer spongy. The cells between them are in active division, 

 but next the plasmodiblast they degenerate. This layer forms 

 the couche 'paraplacentaire of Nolf ^ (Fig. 119). At the placental 

 margin it thins out and disappears. Beneath the epithehoid 

 layer in both areas the cells are drawn out and pseudo-fibrous. 

 The conditions for nutrition resemble those in the very early 

 human ovum, the trophoblast lying against a non-vascular 

 detritus-zone. But in the bat there is strong evidence of 

 phagocytosis. The epiblastic protoplasm, where it is in contact 

 with dead tissue, is " crammed with irregular granules, some 

 fatty and others coloured brown with safranin " (Nolf). The 

 mouths of the glands opening at the non-embryonic pole are 

 filled with debris, and their epithelium is degenerated and 

 desquamated. As previously mentioned, no gland-ducts are 

 present in the coucJie paraplacentaire. The bUnd ends of the 



^ Van der Stricht, "La fixation de I'oeuf de chauve-souris Si I'int^rieur 

 de Tuterus," Verh. d. anat. Gesell., 13 Vers., TUbingen, 1899. 



2 Nolf, "Etude des modiSoations de la muqueuse uterine pendant la 

 gestation cheale murin," Arch, de Biol., vol. xiv., 1896. 



