PROFESSOR W. TURNER ON THE PLACENTATION OF THE APES. 
547 
of blood corpuscles ; and in the less advanced specimen some irregularly-shaped cells, 
three or four times larger than blood corpuscles and with distinct nuclei, were occa- 
sionally seen. The obscure anatomical characters of this stratum made it difficult to 
give an opinion on its nature. From its position on the free surface of the serotina, 
it might be regarded as the coagulated secretion of the utricular glands, but the 
presence of blood corpuscles in it is against such a supposition, and would lead one to 
think that it was coagulated blood. But the paucity of the corpuscles was such as 
to throw doubts upon this interpretation. 
Immediately subjacent to, and in part commingled with, this stratum, was the 
deeper stratum of the compact layer. It was almost entirely composed of cells, the 
nuclei of which were brilliantly stained with hematoxylin, so that it contrasted in 
colour with the superficial stratum. A large proportion of the cells were fusiform, 
and contained elliptical or oval, or at times elongated, nuclei. They were, for the 
most part, arranged with their long axes perpendicular to the free surface of the sero- 
tina. Intermingled with the fusiform cells were rounded and nucleated lymphoid 
corpuscles, which in some localities were more numerous than in others ; also a 
proportion of irregularly- shaped cells, three or four times larger than white blood 
corpuscles. 
The deeper spongy part of the human serotina was thicker than the compact 
stratum. It owed its spongy appearance to the numerous areolae it contained, the 
larger of which were visible to the naked eye. The areolae varied in form, being in 
the vertical sections circular or ovoid, or considerably elongated or triangular, or 
with a greater number than three sides. Sometimes they were closely crowded 
together, and separated by slender thread-like bands of decidual tissue, but at other 
times they were further asunder, and broad bands of the tissue intervened. This 
tissue was continuous with the deeper stratum of the compact layer of the serotina, 
and, like it, consisted of variously formed cells ; but the fusiform corpuscles, more 
especially in the more slender septa between the areolae, were more attenuated than 
in the compact layer. Throughout the serotina the cells were embedded in an 
indistinctly fibrillated matrix. 
The edge of the cut surface of many of the areolae directed towards the enclosed 
space was often quite sharp and distinct, as if bounded by a definite coat, but at other 
times the outline was ragged and wanting in precision, and thin flakes of cells pro- 
jected from the wall into the areola. Some of the smaller areoke having a circular 
outline were unquestionably divided arteries and veins, for they possessed distinct 
coats and contained red blood corpuscles. But blood corpuscles were also contained 
in a number of the spaces possessing an elongated triangular, or even more than 
three-sided form, so that from the nature of then contents they were clearly also 
divided and dilated blood vessels. The corpuscles were at times so abundant as quite 
to fill the areolae, but at other times they only occupied a portion of the space. These 
larger areolae did not possess laminated walls, but the decidual tissue formed their 
