PROFESSOR W. TURNER ON THE PLACENTATION OF THE APES. 
540 
Should this he so, they must be very sparing in numbers. My observations on the 
structure of the spongy layer of the serotina even in the early weeks of pregnancy 
show that the blood sinuses of the decidua constitute a greatly preponderating pro- 
portion of the areolae of the spongy layer : much more so than Leopold’s observations 
would lead one to believe. The employment of injections of the uterine vessels in 
the examination of the decidua in the later months of pregnancy enables one to state 
with certainty that here also the blood sinuses are the dominating, if not the sole, 
factors in the constitution of the areolae. 
In Macacus cynomolgus the areolae so abundantly present in the spongy layer of 
the serotina w T ere obviously not blood sinuses. They did not contain any injection, 
although the injection had fill ed not only the vessels in the muscular coat of the 
uterus, the capillaries, and other vessels of the decidua, but had occupied the maternal 
blood spaces in the interior of the placenta. In the Macacus the veins of the decidua 
do not expand into elongated sinuses as in the human placenta, but retain the form 
of cylindrical tubes, and possess definite walls which can be isolated by dissection from 
the surrounding decidual tissue. The arteries also which penetrate the decidua in 
their course to the placenta do not in the Macacus possess the form of the curling- 
arteries of the human placenta. The areolae in Macacus may probably therefore 
represent the dilated glands in the placental area of the decidua, although their 
epithelial lining had lost its glandular character and had assumed for the most part 
a squamous form. 
But the placental part of the decidua was not limited to the layer which lies 
between the placenta and the muscular coat of the uterus. Both in the human 
placenta and in that of the Ape, processes of the decidua were prolonged into the 
interior of the organ. In the human placenta these processes have been referred to, 
and in some instances imperfectly figured by several observers, as Van der Ivolk,'“ 
Ecker,! Priestley,! anc ^ Kolliker.§ In a paper published in 1872 || I described and 
figured in the human placenta at the full term, bands of the decidua extending from 
the placental layer of the serotina up to the chorion, and separating the lobes or 
cotyledons of the placenta from each other. I named these bands the primary or 
inter-cotyledonary decidual dissepiments. Their junction with the chorion was 
readily seen near the margin of the placenta, and is represented in the plate 
appended to my paper; but nearer the middle of the organ the junction could not 
always be traced. I also observed that these dissepiments could be split into two 
layers, one remaining attached to each cotyledon, and between these layers a utero- 
placental vein was not unfrecjuently situated. Smaller prolongations passing into the 
* ‘ Waarnemingen over Let Maaksel van de Mensclielijke Placenta,’ 1851. 
t ‘leones Physiologic* * * § ,’ 1852-1859. 
X ‘ Lectures on the Gravid Uterus,’ 1860. 
§ ‘ Entwicklungsgeschichte,’ 1st edition, p. 145, 1801. 
|| ‘Journal of Anatomy and Physiology,’ vol. vii., p. 133, plate 5. 
