Evidence of a specific nidation site in ruminants.

The site of umbilical cord attachment in ruminants indicates the limited segment of the uterus where the blastocyst attachment occurs and could have potential significance for locating presumptive nidation sites. Measurements of the site of cord attachment were made on impala (Aepyceros melampus) and common duiker (Sylvicapra grimmia) at several stages of gestation. Both implant only in the right uterine horn although they ovulate from either ovary. Relative to uterine length, cord attachment in impala is somewhat closer to the cervix than it is in common duiker. As pregnancy advances in common duiker, the relative position of cord attachment becomes closer to the tubal end. This relationship was not seen in impala and may perhaps to be attributed inadequate data. Upon extrapolation of the data from common duiker, a presumptive attachment area is suggested for this species. This region is located at about 41% of the distance from the internal cervical os to the uterotubal junction. Similar cord attachment data could be used in any ruminant species to indicate the existence and location of a specific nidation site.