The typical parovarium consists of three parts: a series of vertical tubules; a series of outer tubules free at one extremity; and a larger longitudinal tubule. The vertical tubules range from five to twenty-four in number. They converge somewhat toward the ovary, where they end in blind extremities and become closely associated with the paroöphoron. At the other end they terminate in the larger longitudinal tubule. The series of outer tubules are called Kobelt’s tubes. They are free and closed at the distal extremity, while at the proximal extremity they join the longitudinal tubule. The larger longitudinal tubule is called the duct of Gärtner. It may sometimes be traced traversing the broad ligament to the uterus, and through the walls of this organ and of the vagina to its termination at the urethra. It corresponds to the vas deferens in the male. When persistent in the vaginal wall it may become the starting-point of a vaginal cyst. The vertical tubes of the parovarium are from 0.3 to 0.5 millimeters in diameter. They are occasionally found lined with ciliated columnar epithelium. Usually they contain a granular detritus representing the remains of broken-down epithelium. Cysts may arise from any of the parts of the parovarium. Kobelt’s tubes frequently become distended, and form small pedunculated cysts about the size of a pea. They are of no clinical importance (Fig. 145). They are often observed in operations for ovarian disease, and are very often mistaken for the hydatid or the cyst of Morgagni which springs from the Fallopian tube, and which has already been described. [Illustration: FIG. 170.--Cyst of the parovarium. There is no distortion of the ovary. The Fallopian tube has been much elongated.] The difference between these two varieties of small cysts may be determined by careful examination of the point of origin and by means of the microscope. Sutton states that the cyst of Morgagni has muscular walls and is lined by ciliated columnar epithelium. In the cyst of Kobelt’s tubes the walls are fibrous and the lining is cubical epithelium. Large cysts of the parovarium originate from the vertical or the longitudinal tubules, and usually remain sessile and develop between the layers of the mesosalpinx and the broad ligament. As the cyst grows and separates the layers of the mesosalpinx, it comes into close relationship with the Fallopian tube. This structure, being held by its uterine connection and the tubo-ovarian ligament, becomes stretched across the surface of the cyst and very much elongated. The elongation of the Fallopian tube is a very constant accompaniment of parovarian cysts. The tube may attain a length of 15 or 20 inches. The fimbriæ may also become much stretched and elongated by the traction of the growing cyst, and may attain a length of 4 inches.