NOTES ON STRUCTURE, ETC., OF ELEPHANTS PLACENTA. 7 
We will take these three layers separately. Region A 
fig. 1 is made partly of gelatinous and partly of fibrous 
connective tissue, and contains the blood-vessels, arteries, 
veins, and capillaries having a distinct endothelium. We can 
find no constant line of demarcation that would indicate the 
line of fusion between the amnion and allantois or between 
the walls of the allantois, but there is very generally a 
split, which may represent one or other of these presumably 
originally separate organs. At other points there is however 
undoubted fusion throughout the whole thickness of this region. 
Except in the walls of the blood-vessels only a very few 
nuclei can be found; and of these the greater number lie 
close to the foetal surface. The walls of the blood-vessels 
are greatly thickened and are built up of interlacing bundles 
of large non-striated muscle fibres embedded in the same sort 
of gelatinous and fine fibrous tissue just alluded to. 
These muscle fibres seem to be somewhat peculiar; they 
are In some cases very large. ‘lhey show a wavy outline 
with elongated nucleus which in transverse section is clearly 
seen to be subcentral in position. Hach fibre has a thicker 
middle part which tapers suddenly at each end to a long 
fine fibre. 
The middle layer (region B, fig. 1) is made up of flat- 
tened plates of fibrous tissue which run from the fibrous 
layers (A) and branch repeatedly in all directions in an 
arborescent fashion. Many branches end in small flattened 
foliations within the region (B), others pass through this 
layer and end in thicker less flattened terminations within 
the region (C). It seems possible from the fact that we 
find very thick trunks in region C that some of these lobate 
branches may have been torn off and left in the walls of 
the uterus (fig. 1 wv”, fig. 3 fb., fig. 15 v” and st. v.). 
Wherever these fibrous ramifications are found they contain 
blood-vessels which in the foliation, i.e., in region B, break 
up into a fine network of capillaries, and in the lobate 
terminations, i.e., region C, into a network of vessels which 
are mostly of rather larger calibre, 
