870 REPRODUCTION, DEVELOPMENT, GROWTH AND DEATH [CH. LIX. 



After the rupture of the Graafian follicle, it is filled up with what 

 is known as a corpus luteum. This is derived from the wall of the 

 follicle, and consists of columns of yellow cells developed from the 

 hypertrophy of the epithelial cells of the membrana granulosa; it 

 often contains at first a blood-clot in its centre. The strands of cells 

 get folded and converge to a central mass of jelly-like connective 

 tissue; between the columns there are septa of connective tissue 

 with blood-vessels (fig. 557). The corpus luteum after a time gradu- 

 ally disappears ; but if pregnancy supervenes it becomes larger and 

 more persistent. The following table gives the chief facts in the 

 life-history of the ordinary human corpus luteum, compared with 

 that of pregnancy : 



Ordinary 

 Corpus Luteum. 



Corpus Luteum of 

 Pregnancy. 



At the end of 



three weeks. 



One month . 



Two months 



Six months 



Nine months . 



Three-quarters of an inch in diameter ; central clot reddish ; 



convoluted wall pale. 



Smaller ; convoluted wall j Larger ; convoluted wall bright 



yellow ; clot still reddish. 



bright yellow ; clot still 



reddish. 

 Reduced to the condition 



of an insignificant cica- 



trix. 

 Absent. 



Seven-eighths of an inch in dia- 

 meter ; convoluted wall bright 

 yellow; clot decolorised. 



Still as large as at end of second 

 month ; clot fibrinous ; convo- 

 luted wall paler. 



One half an inch in diameter; 

 central clot converted into a 

 radiating cicatrix ; the external 

 wall tolerably thick and con- 

 voluted, but without any bright 

 yellow colour. 



The ovarian ovum or primary ob'cyte (fig. 558) is a large spheroidal 

 cell surrounded by a transparent striated membrane called the zona 



Nucleus or germinal vesicle. 

 _^ Nucleolus or germinal spot. 



Space left by retraction of 

 protoplasm. 



'--I Protoplasm containing yolk 



spherules. 



Zona pellucida. 



FIG. 558. A human ovum. (Cadiat.) 



pellucida, or zona striata. The protoplasm is filled with large 

 fatty and albuminous granules (yolk spherules), except in the part 



