Pre-partum leucocytic activity and retained placenta.

An investigation concerning the association of the leucocytecotyledon reaction and the expulsion of the placenta is described. The in vitro reaction does not appear to be individual-specific. It is thus possible to determine the activity of the leucocytes against a cotyledon before parturition. The leucocytes of cows which will develop a retained placenta have lowered activity against the chemotactic stimulus of a cotyledon; this reduced activity of the leucocytes can be observed some days before parturition.