NOTES ON STRUCTURE, ETC., OF ELEPHANTS PLACENTA, 19 
well-marked layer (fig. 16), in which they lie closely apposed 
to one another, and only sometimes separated by an intrusion 
of the homogeneous material just spoken of. 
The villi consist of a core of mesoblast with capillaries 
(which in this region stain deeply, almost black with hema- 
toxylin, and give the Prussian blue reaction with ferrocyanide 
of potassium), and are covered by a typical cubical epithelium, 
whose cell-boundaries are distinct and whose nuclei lie close 
to the foetal border of the layer. The cytoplasm generally 
stains very slightly. This, however, is only the case when the 
villi, crowded together, lie against one another. Where they 
abut upon the homogeneous material the epithelium has a very 
different appearance. The cell boundaries are less distinct ; 
the nuclei are much larger, and towards the apices of the 
villi the cells and nuclei are much elongated and the epi- 
thelium shows signs of proliferation (fig. 17). 
As the cells become separated from their point of origin all 
trace of cell-wall disappears, and the nuclei get fainter as 
they are absorbed into the homogeneous material, and ulti- 
mately lose all’ special affinity for nuclear stains, and are 
stained only by such diffuse stains that colour the homo- 
geneous material, if they do not even totally vanish 
(figs. 17 and 23). 
We may say here that although the nuclei throughout all 
parts of Owen’s specimen stain readily as a whole with such 
stains as hematoxylin, thionin, saffranin, carmalum, yet the 
preservation is not sufficiently good to allow of any detail of 
chromatic grains. In no case have we seen an undoubted 
mitotic figure. 
There is no trace of any maternal blood channel outside 
the inner margin of this area consisting of terminations of 
foetal villi. 
To what conclusion must we come as regards this homo- 
geneous material? Is it all foetal: a kind of plasmoditro- 
phoblast ? or is it partly maternal : either cell detritus—e. g. 
uterine epithelium—glandular secretion, or both? 
It stains moderately with hematoxylin carmalum, eosin, 
