Quantitative Cell Counts of the Bone Marrow and Blood and their Secular Variations in the Normal Adult Rat

Abstract

A method for obtaining the absolute number of each type of marrow cell in experimental animals is described in detail. Absolute cell counts are given for the bone marrow and blood of two separate series of rats, one of 40 and the other of 41 animals. Some of the secular variations in cell counts coincided with a change in animal husbandry which might have entailed changes in the genetic constitution of the strain. These changes emphasize the need for frequent observations on control animals during haematological experiments. The femur, tibia and humerus contained similar numbers of nucleated cells but the marrow of the humerus contained fewer non-nucleated red cells. The cell content of marrow of a bone on one side was the same as that in the same bone on the opposite side. Exsangui-nation did not reduce the amount of blood contaminating samples of bone marrow.