2. _Tubo-abdominal Pregnancy._ This name is applied to those cases where the ovule having but just entered the tube, is arrested by an obliteration or constriction of the canal, and there undergoes development. The placenta is attached in the interior of the tube, and the fœtus developed in the abdominal cavity, and both are surrounded by a cyst, the walls of which are partly made up by the walls of the dilated tube. This includes also what has been described as _tubo-ovarian_ pregnancy. 3. _Tubal Pregnancy_ is the most frequent of all varieties of extra-uterine pregnancy. The ovule is here arrested and developed at some spot within the tube, between its abdominal extremity and the point where it enters the uterine walls. The fibres of the enormously distended tube constitute the envelope of the fœtal cyst. 4. _Interstitial Tubo-uterine Pregnancy._ Here the ovule is arrested in that part of the tube that traverses the thickness of the uterine walls. It may remain, during its development, enclosed by the tube, or it may make its way through these and be developed within the muscular fibres of the womb itself. 5. _Utero-tubal Pregnancy_ is a very rare but possible form of extra-uterine pregnancy. The ovule may ingraft itself just at the internal orifice of the canal. “In this variety, the fœtus is found in the abdominal cavity; the cord leaving the umbilicus enters the Fallopian tube, traverses its whole length, and is inserted in the placenta, which is itself attached to the internal surface of the uterus.” The tube has evidently been ruptured, allowing the passage of the fœtus into the peritoneum, while the placenta remained in the uterus. In all these pregnancies, the ovule has originally its proper membranes, the chorion and the amnion. The structure of the walls of the enclosing cyst varies according to the species of extra-uterine pregnancy. As a general rule, the fœtus exhibits nothing peculiar in its development. The most common of the numerous alterations which it may undergo, are putrescent dissolution of its soft parts, and the separation of the various pieces of its skeleton; a complete drying-up or mummification; and transformation of all its tissues into an osseous or cretaceous substance.[39] In the tissues of the mother, new or increased vascularity of those parts where the ovule is attached will be noticed, while the womb will be found to have sympathized with the development of the fœtus by an hypertrophy of its mucous membrane, which, however, does not last more than a few months. A gelatinous substance, a kind of thick, ropy mucus, is also frequently found in the neck of the uterus. These appearances are generally wanting in the womb, where the pregnancy has advanced beyond term.