
PLACENTATION OF THE SEALS. : 285 
decidual bands dipped between the lobules of the placenta, almost up to the 
chorion, and the maternal vessels branched and formed in them a capillary net- 
work. From these bands slender processes passed into the interior of the 
placental lobules, where they formed a lattice-like arrangement of very slender 
trabecule, winding in a sinuous manner through the lobule. These trabecles 
could be pulled out of a lobule with a pair of fine forceps, and in many speci- 
mens the bud-like processes of the chorionic villi lodged in the interstices 
between the trabecles were drawn out along with them. Each trabecle was 
formed of a capillary blood-vessel, surrounded by a thin layer of connective 
tissue, which again was invested by a layer of columnar epithelial cells similar 
to those already described on the free surface of the bands of decidua (fig. 7). 
These cells were very easily detached from the surface of the trabecule, and 
quantities of loose cells floated about the fluid in which the specimens were 
examined. The deep attached end of a cell was often attenuated into a fine 
process. The trabecles were therefore delicate bands of the uterine mucosa, 
and were composed of its several constituents mznus the utricular glands. 
When the uterine face of the placenta, from which the non-deciduous mucosa 
had been peeled off, was examined, a greyish membrane was seen, which at first 
sight seemed as if it might have been a portion of the decidua remaining ad- 
herent to the surface of the placenta, and the exact nature of which required 
some care to determine. It lay in contact with the uterine face of the placental 
lobules ; but instead of being prolonged from the uterine surface of one lobule 
to the corresponding surface of the adjacent lobules, so as to form a continuous 
layer over the whole uterine surface of the placenta, it was continued for some 
distance down the side of each lobule into the substance of the placenta, and 
formed an investment for the individual lobules. Hence the uterine face of the 
placenta was broken up into polygonal areas, each of which corresponded to a 
placental lobule, and the areas were separated from each other by the bands of 
decidua which dipped into the secondary and tertiary fissures of the placenta 
(fig. 6). I then satisfied myself that the greyish membrane belonged to the 
foetal and not to the maternal part of the placenta; for whilst the decidua readily 
peeled off from the one surface of the grey membrane, the other surface was not 
only in immediate contact with the chorionic villi, but was continuous with their 
substance, so that it could not be separated from them without tearing through 
not only the small blood-vessels which passed from the villi mto the greyish 
layer, but its proper connective tissue substance. 
The greyish layer consisted of a tough membrane. When stripped off a 
placental lobule, and examined microscopically, the surface next the villi 
was seen to possess many longitudinal folds, often lying parallel to each other, 
separated by intermediate shallow depressions. This membrane was composed 
of bundles of the white fibres of connective tissue, the fasciculi of which were 
