536 PROFESSOR W. TURNER ON THE PEACENTATION OF THE APES. 
surface cells separated very readily from the subjacent tissue, which could be then 
examined. It was found to consist largely of elongated fusiform nucleated corpuscles, 
such as one is familiar with in the embryonic connective tissue, for they were bigger 
than the similar shaped corpuscles seen in the connective tissue of the adult ; both in 
form and size they resembled the elongated cells of a spindle-celled sarcoma. Inter- 
mingled with the fusiform cells were spherical corpuscles like those of lymph, together 
with a small proportion of oval and elliptical corpuscles somewhat larger than those of 
spherical form. Occasionally thin flakes of protoplasm in which nuclei were imbedded, 
but where a differentiation into distinct cells had not taken place, were observed. 
Blood vessels ramified in the septa between the loculi. They had been filled with 
the red injection and formed a capillary plexus, which was obviously concerned in the 
nutrition of the decidual tissue ; many of these capillaries were of greater calibre than 
one usually finds in capillary networks. 
But in addition to the vessels connected with the nutrition of the decidua, the 
serotina was traversed by veins and arteries passing to the placenta. The utero- 
placental veins passed obliquely through the uterine layer of the decidua serotina, 
and when they reached the placental layer they ran almost parallel to its outer 
surface, which was grooved for their lodgment. They could sometimes be followed 
in close contact with the placental layer for half an inch, or even a greater distance, 
and they were seen to branch two or more times. They were cylindriform vessels, 
smaller in size than the digital veins of the human hand ; they possessed definite 
coats, which with a little care could be separated from the surrounding decidual tissue. 
When these vessels were carefully cut open, their smooth lining membrane was 
recognised, and they were seen to communicate with the interior of the placenta. The 
aperture of communication was crescentic in form, and was directed obliquely, so as to 
act like an imperfect valve. In the posterior lobe of the placenta, where the maternal 
system of vessels was more fully injected, the utero-placental veins were filled with 
the red injection, and when the placenta was gently squeezed, after a vein had been 
opened, the injection could be made to ooze out of the interior of the placenta through 
the crescentic opening into the vein. 
The wall of the uterus did not contain a tortuous arrangement of the branches of 
the uterine arteries so characteristic of these vessels in the human gravid uterus, 
neither were curling arteries to be seen in the decidua serotina. This layer was, 
however, traversed by slender arteries, so fine indeed that it was difficult to isolate 
them from the surrounding decidua. They could be traced up to the placental layer 
of the decidua serotina when they tore through abruptly, so that their exact mode ol 
entering the placenta could not be ascertained ; but it seemed as if the supply of 
arterial blood to the maternal placenta was obtained through numbers of fine arteries 
which pierced the placental layer of the decidua at various points, and quite inde- 
pendently of each other.' 5 ' The red injection of the maternal vessels had freely passed 
* A more explicit description of the utero-placental arteries is given in the Appendix to this Memoir, 
pages 561, 562. 
