658 THE HUMAN BODY. 



the usual recticulum of karyoplasm found in normal resting 

 nuclei (Fig. 8). 



Ovulation. From puberty, during the whole child-bearing 

 period of life, certain comparatively very large Graafian follicles 

 may nearly always be found either close to the surface of the 

 ovary or projecting on its exterior. These, by accumulation 

 of liquid within them, have become distended to a diameter 

 of about 4 mm. (-J- inch) ; finally, the thinned projecting por- 

 tion of the wall of the follicle, which differs from the rest in 

 containing few blood-vessels, gives way and the ovum is dis- 

 charged, surrounded by some cells of the discus proligerus. 

 The emptied follicle becomes filled up with a reddish-yellow 

 mass of cells, and constitutes the corpus luteum, which recedes 

 again to the interior of the ovary and disappears in three or 

 four weeks, unless pregnancy occur; in that case the corpus 

 luteum increases for a time, and persists during the greater 

 part of the gestation period. 



Menstruation. Ovulation occurs during the sexual life of 

 a healthy woman at intervals of about four weeks, and is 

 attended with important changes in other portions of the gen- 

 erative apparatus. The ovaries and Fallopian tubes become 

 congested, and the fimbrias of the latter are erected and come 

 into contact with the ovary so as to receive any ova discharged. 

 Whether the fimbrise embrace the ovary and catch the ovum, 

 or merely touch it at various points and the ova are swept along 

 them by their cilia to the cavity to the oviduct, is not certain. 

 Having entered the Fallopian tube the egg slowly passes on 

 to the uterus, probably moved by the cilia lining the oviduct ; 

 its descent probably takes about four or five days; if not fertil- 

 ized, it dies and is passed out. In the womb important changes 

 occur at or just before the periods of ovulation; its mucous 

 membrane becomes swollen and soft, and minute hemorrhages 

 occur in its substance. The superficial layers of the uterine 

 mucous membrane are broken down, and discharged along with 

 more or less blood, constituting; the menses, or monthly sick- 

 ness, which commonly lasts from three to five days. During 

 this time the vaginal secretion is also increased, and, mixed with 

 the blood discharged, more or less alters its color and usually 

 destroys its coagulating power. Except during pregnancy and 

 while suckling, menstruation occurs at the above intervals, 

 from puberty up to about the forty-fifth year; the periods 

 then become irregular, and finally the discharges cease ; this 



