Retained placenta and leucocytic activity.

In a study of 262 cows, the relationship between the activity of peripheral leucocytes and the expulsion of the placenta was investigated, bearing in mind that the post- partal placenta may be considered as a foreign tissue. The activity of the leucocytes against the cotyledon was examined by determining the presence of chemotaxis in a Boyden Chamber, and by estimating the number of leucocytes in the cotyledon at the time of parturition. It was shown that in the absence of leucocytic activity, retained placenta occurred in 100 per cent of cases. When chemotaxis is used as the sole criterion, positive chemotaxis resulted in an incidence of 2.6 per cent retained placenta and negative chemotaxis in 35.6 per cent.