Summary. The changes induced by infection with the anaemia-inducing (FVA) or the polycythaemia-inducing (FVP) strain of Friend virus on PCV, RBC, reticulocyte counts, red-cell and plasma volume and reticulocyte maturation time were studied in Swiss mice for 7 weeks after viral infection. The data indicated that the increase in total blood volume is mainly due to the augmentation of the spleen and liver blood volume in FVA-disease, whereas it results from the large numbers of red cells produced by the spleen in FVP-disease.
The daily output of reticulocytes was increased four-fold in FVA infected mice, and thirty-fold in FVP infected mice by the 50th day post-infection. The total redcell production for the duration of the experiment was 3 times normal for the FVA group and 13 times normal for the FVP group. A theoretical estimate of the mean red-cell lifespan in infected mice gave 8 1/2 days for the FVP-disease and 22 days for the FVA-disease as opposed to 40 days for the normal mouse.