PELVIS MINOR 499 



Dissection. When the examination of the relations of the 

 uterus is concluded, the dissector should cut through the rectum 

 in the median plane. Then, with the saw, he should divide the 

 sacrum and coccyx to the left of the middle sacral vessels, and 

 when that has been done he should cut through all the remaining 

 tissues in the same plane and separate the two halves of the 

 pelvis. All the remaining stages of the dissection and examina- 

 tion can be carried out on each half separately. 



Vagina. The vagina is the passage which leads from 

 the uterus to the vulva. It is about 75 mm. (three inches) 

 long, and it is widest at its upper end. Its distensibility is very 

 great, to allow the passage of the child during parturition. 

 The direction of the canal, when the bladder and rectum are 

 empty, is from above downwards and forwards, parallel with 

 the plane of the superior aperture of the pelvis minor, so that 

 it forms with the uterus an angle which is open towards the 

 symphysis. Its anterior and posterior walls are closely 

 applied, and in section, therefore, its cavity appears either 

 as a transverse or as a longitudinal slit, according to the 

 direction in which it is divided (Figs. 221 and 224). 



At its upper end the vagina is attached round the neck 

 of the uterus, upon which it ascends farther posteriorly than 

 anteriorly, so that the uterus appears to pierce the anterior 

 wall of the vagina. The shallow sulcus at the upper end of 

 the cavity of the vagina, around the neck of the uterus, is 

 known as the fornix of the vagina. It is formed by the 

 reflection of the mucous membrane of the vagina on to the 

 neck of the uterus, and is separable into anterior, posterior, 

 and lateral parts. The dissector should examine carefully the 

 relations of the fornices. The anterior fornix is in relation 

 with the base of the bladder. 'The posterior fornix is in relation 

 with the recto-vaginal pouch of peritoneum, and therefore an 

 injury of the vagina in that region may open into the lower 

 part of the peritoneal cavity. Each lateral fornix lies 

 below the lower medial angle of the broad ligament, and 

 is in close relation with the ureter, the uterine artery, 

 and the mass of fatty, vascular tissue, previously mentioned as 

 the parametrium. 



The opening of the lower end of the vagina into the uro- 

 genital cleft is partly closed, in the virgin, by the hymen. 

 The hymen is formed by two antero- posteriorly placed 

 crescentic folds of mucous membrane which are united in 

 front and behind. After the hymen has been ruptured, its 



