STRUCTURE OF THE UTERUS. 609 



to its upper part is attached the upper extremity of the vagina, and at 

 its extremity is an opening which is nearly round in the virgin, and 

 transverse after parturition, the os uteri, bounded before and behind 

 by two labia ; the anterior labium being the most thick, and the poste- 

 rior somewhat the longest. The opening of the os uteri is of consi- 

 derable size, and is named the orificium uteri externum ; the canal 

 then becomes narrowed, and at the upper end of the cervix is con- 

 stricted into a smaller opening, the orificium internum.* At this 

 point the canal of the cervix expands into the shallow triangular cavity 

 of the uterus, the inferior angle corresponding with the orificium 

 internum, and the two superior angles, which are funnel-shaped, and 

 represent the original bicornute condition of the organ, with the com- 

 mencement of the Fallopian tubes. In the canal of the cervix uteri 

 are two or three longitudinal folds, to which numerous oblique folds 

 converge so as to give the idea of branches from the stem of a tree ; 

 hence this appearance has been denominated the arbor vitas uterina. 

 Between these folds, and around the os uteri, are numerous mucous 

 follicles. It is the closure of the mouth of one of these follicles, and 

 the subsequent distention of the follicle with its proper secretion, that 

 occasions those vesicular appearances so often noticed within the mouth 

 and cervix of the uterus, called the ovula ofNaboth. 



Structure. The uterus is composed of three tunics ; of an external 

 or serous coat derived from the peritoneum, which constitutes the 

 duplicatures on each side of the organ called the broad ligaments ; of 

 a middle or muscular coat, which gives thickness and bulk to the 

 uterus ; and of an internal or mucous membrane, which lines its in- 

 terior, and is continuous on the one hand with the mucous lining of 

 the Fallopian tubes, and on the other with that of the vagina. In 

 the unimpregnated state the muscular coat is exceedingly condensed in 

 texture, offers considerable resistance to section with the scalpel, and 

 appears to be composed of whitish fibres inextricably interlaced and 

 mingled with blood-vessels. In the impregnated uterus the fibres are 

 of large size, and distinct, and are disposed in two layers, superficial 

 and deep. The superficial layer consists of fibres which pursue a ver- 

 tical direction, some being longitudinal, and others oblique. The 

 longitudinal fibres are found principally upon the middle line, forming 

 a thin plane upon the anterior and posterior face of the organ and 

 upon its fundus. The oblique fibres occupy chiefly the sides and 

 fundus. At the angles of the uterus the fibres of the superficial layer 

 are continued outwards upon the Fallopian tubes, and into the round 

 ligaments and ligaments of the ovaries. The deep layer consists 

 of two hollow cones of circular fibres having their apex at the open- 

 ings of the Fallopian tubes, and by their bases intermingling with 

 each other on the body of the organ. These fibres are continuous 

 with the deep muscular layer of the Fallopian tubes, and indicate the 



* The orificium internum is not unfrequently obliterated in old persons. 

 Indeed, this obliteration is so common, as to have induced Mayer to regard it 

 as normal. 



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