728 GENERATION AND DEVELOPMENT. 



animals is a roundish solid body, of a yellowish or orange 

 colour, and composed of a number of lobules, which sur- 

 round, sometimes a small cavity, but more frequently a 

 small stelliform mass of white substance, from which deli- 

 cate processes pass as septa between the several lobules. 

 Very often, in the cow and sheep, there is no white sub- 

 stance in the centre of the corpus luteum ; and the lobules 

 projecting from the opposite walls of the Graafian vesicle 

 appear in a section to be separated by the thinnest possible 

 lamina of semi-transparent tissue. 



When a Graafian vesicle is about to burst and expel the 

 ovum, it becomes highly vascular and opaque ; and, im- 

 mediately before the rupture takes place, its walls appear 

 thickened on the interior by a reddish glutinous or 

 fleshy-looking substance. Immediately after the rupture, 

 the inner layer of the wall of the vesicle appears pulpy and 

 flocculent. It is thrown into wrinkles by the contraction 

 of the outer layer, and, soon, red fleshy mammillary pro- 

 cesses grow from it, and gradually enlarge till they nearly 

 fill the vesicle, and even protrude from the orifice in the 

 external covering of the ovary. Subsequently this orifice 

 closes, but the fleshy growth within still increases during 

 the earlier period of pregnancy, the colour of the substance 

 gradually changing from red to yellow, and its consistence 

 becoming firmer. 



The corpus luteum of the human female (fig. 21 1) differs 

 from that of the domestic quadruped in being of a firmer 

 texture, and having more frequently a persistent cavity 

 at its centre, and in the stelliform cicatrix, which remains 

 in the cases where the cavity is obliterated, being propor- 

 tionately of much larger bulk. The quantity of yellow 

 substance formed is also much less : and, although the 

 deposit increases after the vesicle has burst, yet it does not 

 usually form mammillary growths projecting into the cavity 

 of the vesicle, and never protrudes from the orifice, as is 



