THE REPRODUCTIVE ORGANS. 



[CH. LVII. 



there are two layers, one lining the follicle, and the other covering 

 the ovum, but the two are close together. A viscid fluid collects 

 between the two layers, and as the follicle increases in size 

 separates them. 



The cells in each layer multiply, so that they are arranged in 

 several strata. The lining epithelium of the follicle is then 

 called the membrana granulosa, and the heaped mass of cells 

 around the ovum, the discus proligerus. The fluid increases in 

 quantity, the follicle becomes tenser and tenser, and finally it 

 reaches the surface of the organ and bursts ; the ovum is thus 

 set free, and is seized by the fringed ends of the Fallopian tube 

 and thence passes to the uterus. 



The bursting of a Graafian follicle usually occurs about the 

 time of menstruation. 



After the bursting of a 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 yellow interstitial cells previously mentioned ; it con- 

 tains a blood clot in its centre. These cells multiply, and their 

 strands get folded and converge to a central strand of connective 

 tissue ; between the columns there are septa of connective tissue 

 with blood-vessels. The corpus luteum after a time gradually 

 disappears ; but if pregnancy supervenes it becomes larger and 

 more persistent (see fig. 613). 



The following table gives the chief facts in the life history of 

 the ordinary corpus luteum of menstruation, compared with that 

 of pregnancy : 



Corpus Luteum of Men- 

 struation. 



At the end of 

 three weeks. 

 One month . 



Two months . 



Six months . 

 Aine months . 



Corpus Luteum of Preg-- 

 nancy. 



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



convoluted wall pale. 



Smaller ; convoluted ; Larger ; convoluted wall bright 

 yellow ; clot still reddish. 



wall bright yellow ; 

 clot still reddish. 

 Reduced to the condi- 

 tion of an insignifi- 

 cant cicatrix. 



Absent. 



Seven-eighths of an inch in dia- 

 meter ; convoluted wall bright 

 yellow ; clot perfectly de- 

 colorised. 



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; theexternal 

 wall tolerably thick and con- 

 voluted, but withoutany bright 

 vellow colour. 



