10 
AN EARLY HUMAN OVUM 
up somewhat prominently from the rest of the membrane. The papilla 
so produced (Figure i) at its right margin slightly overhung a deep furrow, 
but at the ends and on the left side it sloped gradually down to the 
general level of the surrounding membrane. This elevated area measured 
roughly 6 mm. by 3 mm. ; it was nearly 3 mm. in thickness, wdiile the 
rest of the membrane did not exceed 2 mm., and was for the most part 
thinner. About the centre of the papilla there was a circular mark 
like a very shallow dimple, and of lighter colour than the rest of the 
surface. The adjacent tissue was of deep red colour as if congested, and 
Figure I. Portion of Decidual Membrane containing the Ovum; 
SLIGHTLY MAGNIFIED. 
The prominent lobule is the actual site of implantation. The indistinct dimple¬ 
like mark slightly below the centre of the lobule corresponds to the position of 
the blastocyst. The darker shading represents congestion, and the dark spot 
above the dimple is a haemorrhage. 
a still darker patch above the circular mark was regarded as probably 
due to haemorrhage into the membrane. The area thus described is very 
similar in appearance to the lobule of decidua in which the ovum investigated 
by Leopold in 1906 was enclosed. 
Although it seemed improbable that after twenty hours’ immersion 
in a mixture of blood and urine the fixation of the preparation could 
be satisfactory, the membrane was placed in absolute alcohol, this medium 
having before been found to be the most satisfactory fixative in similar 
circumstances. After thirty hours the lobule was excised, imbedded in 
paraffin, and cut by William Price, the laboratory attendant, into a perfect 
