THE OVARY. [BOOK iv. 



way tit the ovum, loading its cell-substance with substances 

 which form the yolk. 



933. The cumulus, with the ovum within it, is placed, as 

 we have said, cxccntrically in the cavity of the follicle, and indeed is 

 so j.laccd that the ovum lies in the region of the follicle nearest to 

 the surface of the ovary. As the follicle in course of growth 

 becomes larger and more distended, it not only occupies a con- 

 siderable portion of the whole bulk of the ovary, but encroaches 

 on the germinal zone owing to the wall of the follicle near which 

 the ovum lies becoming more and more superficial in position 

 This part of the wall also becomes thinner and thinner, and ulti- 

 mately bursts, the ovum with the cumulus being discharged from 

 the interior of the follicle, and received, as we shall see, into the 

 mouth of the adjoining Fallopian tube. 



Before this ejectment occurs, changes other than those of mere 

 growth or enlargement take place in the ovum itself. Into those 

 changes we cannot enter here, and must merely content ourselves 

 with stating that the nucleus and other parts of the ovum-cell 

 behave very much as if the ovum were about to divide ; there are 

 movements and transformations of the nuclear elements resem- 

 bling in many ways those seen in a cell about to multiply by 

 division ; but these do not issue in an actual division of the ovum, 

 they lead merely to the casting out of a portion of the old nucleus, 

 the germinal vesicle, in the form of bodies known as ' polar globules,' 

 and to the conversion of the remainder into a new nucleus, the 

 pro-nucleus. To carry on these changes to a division of the ovum 

 and cellular multiplication, a new influence must be brought to 

 bear, that of the male element in impregnation. 



934. The bursting of the follicle in the discharge of the 

 ovum is accompanied by rupture of the small blood vessels of the 

 follicular walls and, at times but not always, blood escapes into 

 the cavity of the collapsed follicle. A new growth now takes 

 place ; the cells of the membrana granulosa multiply rapidly, the 

 connective tissue elements of the walls also multiply, sending 

 vascular ingrowths into the interior, until the follicle becomes a 

 solid mass of cells traversed by radiating septa of stroma, the 

 centre being occupied, when haemorrhage into the follicle has 

 taken place, by the effused blood, the hemoglobin of which is soon 

 converted into hsematoidin. After a while the growth of cells and 

 stroma is arrested, and fatty degeneration of the cells takes place. 

 The fat is coloured with a yellow pigment, lutein, about which 

 there has been much dispute but which appears to be distinct 

 from bilirubin ; and this gives a yellow colour to the whole mass, 

 which is now called a corpus luteum. The degeneration is followed 

 by absorption, and ultimately a mere scar is left. 



Whenever an ovum is discharged changes of this kind follow, 

 but if the ovum be impregnated they are generally exaggerated. 

 The membrana granulosa is much folded during its excessive 



