In describing the lesions of laceration of the cervix and cervical catarrh, frequent mention has been made of the cervical erosion or the catarrhal patch. The erosion, or red granular area, surrounding the external os seems to be caused by various factors. In laceration it is due to the eversion and exposure of the normal cervical mucous membrane, and perhaps to slight proliferation of the cylindrical cells of this mucous membrane on to the mucous membrane of the vaginal aspect of the cervix. In cervical catarrh it is caused by swelling and prolapse of the mucous membrane of the cervical canal, and extension of the inflammatory process beyond the limits of the external os, with partial desquamation of the squamous cells. There are other cases, however, in which the erosion appears to be congenital. Such erosions have been observed by Fischel and other investigators surrounding the external os in new-born infants. Erosion of this character has been found, in a more or less marked degree, in 36 per cent. of new-born infants. Microscopically, these erosions appear to be a direct continuation of the mucous membrane of the cervical canal. They are covered with a single layer of cylindrical epithelium, and they possess mucous glands, resembling in these features the cervical mucous membrane, and not the mucous membrane of the vaginal aspect of the cervix, which, it will be remembered, is covered with squamous epithelium and contains no glands. This congenital erosion usually is of very limited extent, but in some cases it covers the greater part of the vaginal aspect of the cervix, and may then give rise to decided symptoms. The condition is due to imperfect development of the external os. In the well-formed woman there is, at the external os, a sharp line of demarcation between the squamous epithelium of the vaginal aspect and the cylindrical epithelium of the cervical canal. In the congenital erosion the epithelium of the canal extends beyond the limits of the external os, and meets the squamous epithelium at a lower level than normal. Such congenital erosions usually give rise to no trouble, though perhaps they predispose the woman to cervical catarrh as a result of exposure of the mucous membrane. In extreme cases, however, in which the cylindrical epithelium of the cervical canal persists over the greater part of the vaginal cervix, and in which the glandular elements of the canal are found on the vaginal aspect, a distinct pathological condition arises. The symptoms of this condition resemble closely those of laceration of the cervix with ectropion. There is backache, a feeling of weight in the pelvis, and perhaps some ovarian pain. In addition, the woman complains of a leucorrhea presenting the characteristics of the cervical mucus. Decided nervous and digestive disturbances may be present.