894 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



but not wholly decisive literature upon the subject in the human being has 

 been written. It is a common belief, originating in the seventeenth century, 

 that ovnlation in woman is a periodic phenomenon occurring regularly every 

 month and contemporaneous with the occurrence of the menstrual flow, and 

 numerous post-mortem observations of the presence in the ovary of freshly- 

 discharged Graafian follicles at the menstrual period afford evidence of the 

 frequent coincidence of the two phenomena. But ovulation at the time of 

 menstruation, though probably usual, is not exclusive of ovulation at other 

 times, for intermenstrual observations of fresh ovarian scars are not rare, and 

 prove without doubt that discharge of an ovum may occur at any time between 

 two successive periods (see under Menstruation, p. 895). Graafian follicles 

 develop even during infancy ; most of them, and perhaps all, retrograde with- 

 out discharging their ova, but the occasional instances of pregnancy at the ages 

 of seven, eight, or nine, prove that ovulation may occur during childhood. 

 Ovulation usually begins at puberty, its commencement thus coinciding with that 

 of menstruation, and continues until the climacteric. After the climacteric it 

 may occur in exceptional cases, although here, as before puberty, retrogressive 

 degeneration of the Graafian follicles is the rule. It is commonly believed that 

 ovulation is at a standstill during both pregnancy and lactation. The un- 

 doubted possibility of a pregnancy originating during lactation would, how- 

 ever, seem to prove the possibility of ovulation during the latter period. It is 

 not decided whether removal of the uterus does away wholly with ovulation. 



The Fallopian Tube. Each of the Fallopian tubes (Fig. 309, F. f), or 

 oviducts, opens into the peritoneal cavity about one inch from the correspond- 

 ing ovary. Around the opening is an expanded fringe of irregular processes, 

 thefimbrice (/), one of which is attached to the ovary. The length of the tube is 

 between three and four inches, and the opening into the uterus is extremely 

 small. The chief structures in the walls of the oviducts that are of physio- 

 logical interest are the double layer of plain muscle, an outer longitudinal 

 and an inner circular coat, longitudinal fibres from which pass also into the 

 fimbrise ; and the cilia with which the tube is lined throughout, and which are 

 present also upon the inner side of the fimbrise. The direction of the ciliary 

 movement is from the ovary toward the uterus. The primary function of the 

 Fallopian tubes is to convey ova from the ovary to the uterus ; they also con- 

 vey spermatozoa in the reverse direction ; and within them the union of ovum 

 and spermatozoon usually takes place. 



The mechanism of the receipt of the ovum by the tube is not fully under- 

 stood. After ovulation the ovum is slightly adherent to the surface of the 

 ovary by the agency of the viscid liquor folliculi. It is possible, but it has 

 not been proved, that in the human being, as has been seen in some animals, 

 the expanded, fimbriated end of the Fallopian tube clasps the ovary when 

 the egg is discharged. The passage of the ovum into the tube is probably 

 brought about by the cilia lining the fimbrise. Once within the tube, the 

 ciliary action, assisted perhaps by contraction of the muscular fibres in the 

 walls, carries the ovum slowly along toward and finally into the uterus. In 



