Fig. [72].—Normal Portio Vaginalis.
Fig. [73].—Conoidal Portio Vaginalis.
In conception, the cervix uteri subserves the important function of providing for the free passage of the spermatozoa to the interior of the uterus; and when we consider the nature of the processes of sexual intercourse and fertilization, and more especially when we bear in mind that normally the two lips of the cervix and the upper segment of the vagina form a chamber for the retention of a portion of the seminal fluid in contact with the os uteri externum, we are readily led to assume that any great abnormality, in size of the cervix (enlargement or diminution), in its shape (malformation), or in its position (displacements—flexion, version, or prolapse), or, finally, stenosis of the cervical canal,—may offer mechanical hindrances to conception. And experience shows that this assumption is justified, at any rate as regards conical elongation of the portio vaginalis (Fig. [73]), as regards an apron-shaped or beak-shaped hypertrophy of the anterior lip of the cervix (Figs. 74 and 75), as regards flexion upwards of the elongated cervix, and also as regards stenosis or obliteration of the external or the internal os; although the reservation must be made that no matter how unfavourable the shape of the portio vaginalis, no matter how extensive the changes in the cervix uteri, as long as a permeable upward passage for the spermatozoa exists, conception is still possible, and in exceptional cases may occur.
Fig. [74].—“Apron-shaped” Vaginal Portion. a. Greatly elongated anterior lip; b. Shorter posterior lip of the cervix.
Fig. [75].—“Beak-shaped” Vaginal Portion. Posterior aspect.
When the cervix is hypertrophic and greatly enlarged, and the vaginal fornix consequently much elongated, conception is rendered difficult, for the reason that in such cases, either the semen rapidly flows out of the vagina, or else a proper juxtaposition between the penis and the external os no longer occurs, and the semen is ejaculated at some distance from the os. The change in the shape of the portio vaginalis, and also the elongation of the cervical canal, are additional obstacles to the entrance of the spermatozoa into the interior of the uterus; as regards the former condition, in nulliparae the portio vaginalis is commonly conical, or pointed, whilst the external os is very small, thus rendering the passage of the spermatozoa a difficult matter; but in parous women, it is lobulated, owing to the presence of deep fissures, whereby the penis is conducted into the vaginal fornix, and the ejaculation of the semen in this locality is facilitated. Hence, such hypertrophy of the cervix and the portio vaginalis often coincides with the occurrence of sterility. The hypertrophy is less apt to cause sterility when it is limited to one lip of the cervix, unless, indeed, the affected lip (more commonly the anterior) is so greatly enlarged that it bends over and occludes the external os, whilst conducting the penis into the fornix and away from the orifice. Cases have been known in which a single lip of the cervix was hypertrophied to such an extent as to protrude between the labia.
The commonest malformation of the cervix is the conical cervix, when the cervix is not merely elongated, but tapering; associated with this condition is usually found a notable diminution in size of the os uteri externum. According to Sims we find “conical cervix in 85% of all cases of natural sterility.” According to the same author, even in the absence of the conical form of cervix, “sterility is probable in cases in which the portio vaginalis projects fully half an inch into the vagina; if the cervix projects more than one inch, sterility almost inevitably results; whilst if elongation is even greater than this, so that the vaginal portion measures from one and a half to two inches, sterility is absolutely certain.”