REPRODUCTION 743 



The Fallopian Tubes. The Fallopian tubes are about 12 centimeters 

 in length and extend from the upper angles of the uterus to the ovaries. 

 Each tube is somewhat trumpet-shaped, the narrow portion being close to 

 the uterus, the wide portion close to the ovary. The outer extremity of the 

 tube is expanded and subdivided, and presents a series of processes termed 

 fimbriae, one of which is attached to the ovary. The tube consists of three 

 coats an external or fibro-serous; a middle or muscle, the fibers of which 

 are arranged longitudinally and circularly; and an internal or mucous, which 

 is folded longitudinally. The surface of the mucous coat is covered with a 

 layer of ciliated epithelial cells, the direction of motion of which is toward 

 the uterus. 



The Uterus. The uterus is pyriform in shape and divided into a body 

 and neck. It measures, before the first pregnancy, about 7 cm. in length, 

 5 cm. in breadth and 2^ cm. in thickness. A frontal section of the uterus 

 shows a central cavity which in the body is triangular in shape, in the neck 

 oval or fusiform (Fig. 325). At the upper angles of the uterus the cavity is 

 continuous with the cavity of each Fallopian tube. At the junction of the 

 body and the neck, the cavity presents a constriction, the internal os. The 

 constriction at the end of the neck is known as the external os. The walls of 

 the uterus are extremely thick and composed of non-striated muscle-fibers 

 arranged in a very complicated manner. The interior of the uterus is lined 

 by mucous membrane covered with cylindric ciliated epithelial cells, the 

 motion of which is toward the external os. Tubular glands are found in 

 large numbers in the mucous membrane lining the cavity, while racemose 

 glands are found in the mucous membrane lining the neck. Owing to the 

 flattening of the uterus from before backward the walls are almost in contact 

 and the cavity almost obliterated. 



The Vagina. The vagina is a musculo-membranous canal, from 12 to 

 1 8 cm. in length, situated between the rectum and bladder. It extends 

 from the surface of the body to the brim of the pelvis, and embraces at its 

 upper extremity the neck of the uterus. 



Ovulation. After the establishment of puberty a Graafian follicle 

 develops and ripens or matures periodically, usually every twenty-eight days. 

 During the time of maturation the follicle increases in size, from an augmen- 

 tation of its fluid contents, and approaches the surface of the ovary, where it 

 forms a projection varying from 6 to 12 mm. in size. When maturation is 

 complete the vesicle ruptures, and the ovum and liquid contents are discharged. 

 The ovum, by a mechanism not fully understood, is received by the fimbriated 

 extremity of the Fallopian tube and enters its cavity. The ovum is then 

 transferred through the tube by the peristaltic contraction of its muscle- 

 fibers and by the action of the cilia of its lining epithelium. The time 

 occupied in the transference of the ovum from the ovary to the interior of the 

 uterus has been estimated to be from four to ten days. 



Either at the time of, or very shortly after, its discharge from the follicle, 

 the ovum, and more especially the nucleus, undergoes a series of histologic 

 changes which eventuates in an extrusion of a portion of the chromatin 

 material. The extruded portions are known as the polar bodies. The non- 

 extruded portion of the chromatin material is known as the female pronu- 

 cleus or germ nucleus. The chromosomes are reduced to one-half the somatic 

 number. The succession of changes which the nucleus undergoes is termed 



