_His_ has formulated the theory that in the human species fertilization is possible only in the uppermost segment of the tube; an assumption that is probable enough, but cannot be regarded as definitely established. An analogy certainly exists among the lower divisions of the animal kingdom, for _Coste_, _His_, and _Ohlschläger_ have proved that an ovum which passes through the Fallopian tube without being fertilized, undergoes notable alterations. Further, _Coste_ has shown, in the case of the ovum of the domestic fowl, that this is no longer capable of being fertilized after it has passed through the upper segment of the oviduct. Other authorities, however, namely _Löwenthal_, _Mayrhofer_, and _Wyder_, oppose the extension of this rule to the human species. _Löwenthal_ assumes that in the human female, fertilization ordinarily occurs in the cavity of the uterus, in the wall of which the unfertilized ovum has already embedded itself; and he supports his contention by the statement that spermatozoa are not to be found in the Fallopian tubes or on the surface of the ovaries. _Mayrhofer_ and _Wyder_ point out that the movement of the cilia of the ciliated epithelium is in the interior of the uterus in an upward direction, but in the Fallopian tubes is downwards in the direction of the uterus. The contention of _Löwenthal_ was disproved by _Birch_ and _Hirschfeld_, who, in a prostitute dying during the act of intercourse, found, fifteen hours after death, living spermatozoa in the Fallopian tubes. On the other hand, more recent investigations, those, for instance, of _Hofmeier_, _Mandl_, and _Bonn_, have confirmed the data given above with regard to the direction of the ciliary movement in the interior of the genital passages. Moreover, _O. Becker_ has shown that the ciliated epithelium of the tubes extends over the fimbriae and even on to the adjoining pavement epithelium of the peritoneum; and he believes that the ciliary movement of this region keeps up a constant current, the purpose of which is to sweep the ovum into the ostium of the tube, and thence down towards the uterus. _Lode_ has adduced positive experimental evidence of the occurrence of such a movement of translation. The general result of anatomical investigation is, that the conjugation of the ovum with the spermatozoön takes places in the ampulla of the Fallopian tube; but it is established that fertilization may also take place lower down in the tubes, or in the uterine cavity, or even on the surface of the ovary, _i. e._, in the abdominal cavity.