726 THE REPRODUCTIVE ORGANS 



When fully formed, the corpus luteum of mammals is a roundish solid 

 body, of a yellowish or orange color, and composed of a number of lobules, 

 which surround, sometimes a small cavity, but more frequently a small 

 stelliform mass of substance, from which delicate processes pass as septa 

 between the several lobules. The processes gradually change till they 

 nearly fill the cavity of the follicle, 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 color of the substance gradually changing to yellow, and its consistency 

 becoming firmer. After the orifice of the follicle has closed, the growth 

 of the yellow substance continues during the first half of pregnancy, till 

 the cavity is reduced to a comparatively small size or is obliterated; in the 

 latter case, merely a white stelliform cicatrix remains in the center of the 

 corpus luteum. 



The first changes of the internal coat of the ovarian follicle in the proc- 

 ess of formation of a corpus luteum seem to occur in every case in which an 

 ovum escapes. If the ovum is impregnated, the growth of the yellow sub- 

 stance continues during nearly the whole period of gestation and forms the 

 large corpus luteum commonly described as a characteristic mark of 

 impregnation. 



The significance of the corpus luteum is found in the belief that it is the 

 portion of the ovary especially concerned in the production of an internal 

 secretion that affects the uterus, especially stimulating it at and before the 

 menstrual period. 



Menstrual Life. The occurrence of a menstrual discharge is one of 

 the most prominent indications of the commencement of puberty in the fe- 

 male sex; though its absence even for several years is not necessarily at- 

 tended with arrest of the other characters of this period of life or incapability 

 of impregnation. The average time of its first appearance in females of 

 this country and others of about the same latitude is from fourteen to fifteen: 

 but it is much influenced by the kind of life to which girls are subjected, 

 being accelerated by habits of luxury and indolence, and retarded by con- 

 trary conditions. Its appearance may be slightly earlier in persons dwelling 

 in warm climates than in those inhabiting colder latitudes. The menstrual 

 functions continue through the whole fruitful period of a woman's life, and 

 usually cease between the forty-fifth and fiftieth years, which time is known 

 as the climacteric. Menstruation does not usually occur in pregnant women. 



