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PROFESSOR ARTHUR ROBINSON ON 
tion, especially associated with the accumulation of lipoid substances ; increase of 
the thickness of the oolemma ; and the migration of the nucleus to the periphery 
of the ovum, where it lies in close apposition with the oolemma. 
It has already been noticed that during the same period the outlines of the 
follicle cells become gradually more distinct ; other changes which occur in the 
follicle cells, including changes of structure and alterations in the positions of 
the nuclei, will be dealt with more fully in a subsequent section. 
The Post-inseminal Growth and the Ktjpture of the Follicles. 
After insemination the most obvious changes occur in the region of the ovarian 
cumulus. So far as the ovum is concerned the essential changes are the formation 
of the first maturation spindle, followed by the formation of the first polar body 
and the second maturation spindle. These changes only occur, normally, after 
insemination ; they may occur, however, in ova in the follicles of non-inseminated 
animals, but only occasionally, and then always accompanied by other phenomena 
which indicate abnormal conditions. 
The most striking changes, independently of the maturation phenomena in the 
ovum, are those which take place in and amidst the cumulus epithelium. 
About eighteen hours after insemination, or later, the secondary liquor folliculi, 
which had already appeared in small amount in the later period of pre-inseminal 
growth, increases rapidly. As the secondary liquor folliculi is augmented the 
peripheral cells of the projecting part of the cumulus and the more internal cells 
of the basal portion are dispersed in all directions (figs. 17, 18, 19, 20, PI. Ill ; figs. 
21, 22, 23, 24, PI. TV). The nuclei of the dispersed cells show indications of 
degeneration, the protoplasmic processes by which the cells were connected are 
destroyed, and many of the cells break down and disappear. At the same time 
the periovular cells of the cumulus are transformed into a very beautiful corona 
radiata. As the corona radiata is developed all the periovular cells become club- 
shaped. The thin ovular ends of the cells remain connected with the oolemma, 
and the nuclei migrate to the enlarged peripheral ends of the cells (figs. 41, 42, 43, 
44, PI. VII ; fig. 45, PI. Yin). 
By the continued increase of the secondary liquor folliculi the membrana interna 
is separated from the follicular cells. Sometimes this separation is complete, but 
in the majority of cases it is, probably, only partial. When the cumulus is situated 
at the superficial part of the follicle the membrana interna, as it is stripped from the 
follicular epithelium, is simply pushed towards the deeper part of the follicle (fig. 22, 
PI. IY), but when the cumulus lies in the deeper part of the follicle, the secondary 
liquor folliculi pushes its way between the separated membrana interna and the 
follicular epithelium, till it reaches the superficial part of the follicle (figs. 18, 19, 20, 
PI. Ill ; figs. 21, 23, 24, 25, PL IY). In the meantime the superficial part of the 
