The Fetal Membranes 69 



this filter, so long as it is healthy, no solids or other visible 

 substances ordinarily pass. Bacteria are not known to pass 

 this filter while it is healthy. Researches show further that 

 rarely or never do the hypothetical antibodies pass this 

 filter, so that a mother may be highly infected with a given 

 bacterium and her blood react strongly by agglutination or 

 complement-fixation to such organism, but the blood of her 

 new-born fails to react. The contact between the fetal and 

 the maternal epithelium is so intimate, that no infection nor 

 foreign substance may readily exist between them. Hence 

 in the placental area, so long as the structures are healthy, 

 so far as known, infection can not pass from the mother to 

 the fetus through the placental filter, nor can infection in- 

 vade the fetus from the uterine cavity by passing between 

 the two fetal structures, and thence gain the fetal cir- 

 culation, without having first attacked and severely dam- 

 aged the placental structures themselves. 



The Utero-Chorionic Space. There is, however, a 

 more vulnerable area through which bacterial invasion of 

 the embryonic sac may occur. There are about one hundred 

 functioning cotyledons in the healthy gravid uterus of the 

 cow. Each of these cotyledons, in the slaughtered animal 

 (they are doubtless much thicker in the living animal while 

 they are distended with blood) is one to one and one-half 

 inches in its perpendicular diameter while the peduncle of 

 the cotyledon measures an inch or more, thus tending to 

 push the chorion away from the non-placental endometrium 

 for a distance of two inches. The one hundred cotyledons 

 with their stalks serve as a great colonnade producing a 

 vast space between the non-placental areas of the uterus and 

 chorion, designated the utero-chorionic space. At full term 

 of pregnancy, the uterine mucosa offers an area of approxi- 

 mately fifteen square feet. In this space, as in the non- 

 gravid uterus, bacteria commonly exist and need only to in- 

 vade successfully the thin non-placental chorion and adher- 

 ent amnion to gain the amniotic cavity and fluid. With the 

 fluid, the fetus swallows any bacteria present. But the bac- 

 teria have other interesting portals of entry, the importance 



