THE VAGINA 687 



and veins are found in large numbers in the outer part so as to form almost a 

 special vascular coat. The mucous membrane of the uterus is composed of col- 

 umnar ciliated epithelium, which extends also to the interior of the tubular 

 glands, of which the mucous membrane is largely made up. In the cervix of 

 the uterus the mucous membrane is arranged in permanent longitudinal folds, 

 palma plicatce. The glands of this part branch repeatedly, and extend deeply 

 into the substance of the cervix. The body has numerous simpler tubular 

 glands. The glands are also lined with ciliated epithelium. They secrete a 

 thick glairy mucus, resembling white of egg. 



The Vagina. The vagina is a membranous canal 8 to 10 cm. long, 

 extending obliquely downward and forward from the neck of the uterus, 

 which it embraces, to the external organs of generation. It is lined with 

 mucous membrane, covered with stratified squamous epithelium, which in 

 the ordinary contracted state of the canal is thrown into transverse folds. 

 External to the mucous membrane, the walls of the vagina are constructed 

 of unstriped muscle and fibrous tissue, within which in the submucosa, 

 especially around the lower part of the tube, is a layer of erectile tissue. The 

 lower extremity of the vagina is embraced by an orbicular muscle, the sphincter 

 vagina. The external organs of generation are the clitoris, the labia interna 

 or nymphce; and, the labia externa or pudenda, formed of the external integu- 

 ment, and lined internally by mucous membrane. Numerous mucous follicles 

 are scattered beneath the mucous membrane of the external organs of genera- 

 tion; and two larger lobulated glands, the glands of Bartholin, analogous to 

 Cowper's glands in the male, are located at the sides of the lower part of the 

 vagina. The ducts of these glands are about 1 2 mm. long and open immediately 

 external to the hymen at the mid-point of the lateral wall of the vaginal orifice. 



Ovulation and Menstruation. In the process of development in the 

 ovary, the individual Graafian follicle increases in size and gradually ap- 

 proaches the surface of the ovary. When fully ripe or mature, it forms a 

 little projection on the exterior. Coincident with the increase in size, which 

 is caused by the augmentation of its liquid contents, the external envelope 

 of the distended vesicle becomes very thin and eventually bursts. The ovum 

 and fluid contents of the vesicle escape on the exterior of the ovary, whence 

 they pass into the Fallopian tube. 



In man and mammals ovulation apparently occurs only at certain periods. 

 These periods seem to precede or occur during the changes in the woman 

 that constitute the phenomenon of menstruation, or, in the lower mammals, 

 of heat. 



That ovulation and discharge occur periodically, and only during the 

 phenomenon of heat, in the lower mammalia, is made probable by the facts 

 that, in all instances in which Graafian vesicles have been found presenting 

 the appearance of recent rupture, the animals were at the time or had recently 

 been in heat. There are few authentic and detailed accounts of Graafian 



