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PROFESSOR ARTHUR ROBINSON ON 
in the majority of the cases, the ovaries of opposite sides were fixed in different 
fluids, the proportion of right and left ovaries fixed in similar fluids was about 
the same. 
Structure. 
The cortex and the medulla of the ovary of the ferret are very sharply defined 
(fig. 61, PI. X). The medulla is reticular in character, and it is continuous with the 
extra-peritoneal connective tissue at the hilum of the ovary. Through it pass 
numerous blood and lymph vessels, and in it lie cords of interstitial cells which are 
connected with the interstitial substance of the cortex, and two sets of tubules. The 
tubules of one group, which are irregular , in number and size, are similar to the 
occasional tubules which are met with in the cortex (fig. 63, PI. X). The other set, 
consisting of tubules which are of smaller size, lie near the hilum, and are continuous, 
through it, with the tubules of the epovarium, which lies in the mesentery of the 
uterine cornu. The latter are similar, in all essential respects, to the tubules 
described by Winiwarter (43) in the cat. 
The cortex is surrounded by the so-called germinal epithelium, internal to which 
is a definite tunica albuginea. The tunica albuginea consists of spindle-shaped cells, 
and of fibrils which run, for the most part, parallel with the surface of the ovary, 
but which bend inwards, at intervals, to become continuous with strands of spindle- 
shaped cells which pass through the cortex from the tunica albuginea to the medulla, 
with both of which they are continuous. Most of the primitive ovarian follicles lie 
in the spindle-cell strands of the cortex, which are particularly numerous near the 
hilum of the ovary, but some are found also in the tunica albuginea (fig. 3, PI. I). 
The main mass of the cortex consists of interstitial cells, which are divided into 
columns and nests by lamellae of spindle cells (figs. 61, 63, PI. X). 
The interstitial cells vary considerably in size, but they all possess the typical 
polygonal body and the large round nucleus. 
The blood and lymph vessels of the cortex lie either in the tunica albuginea or 
in the spindle-cell strands, into which they penetrate after passing through the 
medulla of the ovary. 
The Ovarian Follicles. 
When the primitive ovarian follicles are first recognisable, as such, in the adult 
ovary, each follicle consists of an ovum, surrounded by a single layer of flattened 
cells, which constitute the primitive capsule, and which are the progenitors of the 
follicular epithelium. 
The ovum is spherical or ovoid ; its nucleus is large, round, and excentric ; it 
always contains one large spherical nucleolus ; and sometimes, though rarely, two 
nucleoli are present. In the portion of the ovum not occupied by the nucleus there 
are numerous granules of varying shape, size, and chemical constitution (figs. 4, 4a, 
5, PI. I). The granules are especially numerous at the pole opposite to the nucleus, 
