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PROFESSOR ARTHUR ROBINSON ON 
PL II). This condition persists until some time after the follicles become vesicular, 
then, as the follicles are distended by the accumulation of the liquor folliculi in their 
cavities, they become more spherical, but are never completely spherical. As the 
antrum folliculi grows the rapidity of the multiplication of the nuclei of the follicular 
epithelium increases, and it is most rapid in the region of the ovular cumulus ; 
simultaneously the outlines of the follicle cells become more distinctly defined, and 
the nucleus of the ovum migrates to a peripheral position (fig. 16 , PI. Ill; figs. 40 , 
41 , 42 , PL VII). 
Antrum Folliculi and Primary Liquor Folliculi. 
The majority of the follicles begin to become vesicular as soon as the nuclei of the 
follicular epithelium are arranged in three layers in the greater part of the area of 
the follicle, and, as a rule, the first indications of cavity formation take place at the 
poles of the follicles (figs. 10, 11, 12, Pl. II). 
The first indications of the formation of the cavity of a follicle are the appearance 
of numerous small independent spaces at one or other, or both, poles of the follicle. 
Presumably the spaces are formed by the accumulation of a more fluid substance 
between the cell territories ; at all events the spaces are separated from one another 
by strands of protoplasm which are continuous with the protoplasmic substance 
around the adjacent nuclei. As the fluid-filled spaces distend the protoplasmic 
strands between them become reduced to extreme tenuity ; but, even when the 
follicle has attained the full growth of which it is capable before insemination, and 
its cavity is fully distended, it is obvious, when the fixation and staining have been 
successful, that the so-called liquor folliculi is in reality a fluid-filled, meshwork 
(fig. 13 , Pl. II ; fig. 14 , Pl. III). The extremely fine strands of the reticulum 
anastomose freely with one another, and they are connected on the one hand with 
the cells of the ovular cumulus, and on the other with the follicle cells which form, 
together with the cumulus cells, the peripheral wall of the cavity of the follicle. As 
the term liquor folliculi is established, and as the fluid part of the content of the 
cavity is undoubtedly preponderant, I propose to call this first formed, fluid-filled, 
meshwork the 'primary liquor folliculi, for, as I shall show later, a secondary and a 
tertiary content of the cavity can be distinguished, each of which has its distinctive 
characteristics. 
The ovarian cumulus, as is well known, is the mass of cells in which the ovum is 
embedded. The greater part of it projects into the cavity of the follicle, and the 
remainder, which forms the base of the cumulus, is directly continuous, either over 
a broad area or by means of a relatively narrow stalk, with the lining follicular cells. 
In ferrets and ferret-polcat hybrids the ovular cumulus is generally situated in 
the deeper part of the follicle, that is, the part furthest away from the surface of the 
ovary, but in some cases it lies at the most superficial part of the follicle. 
As the cavity of the follicle attains its full growth a membrane, which may be 
