Fig. 7. Hematocrit of female mice from a study reported elsewhere (Swallow et al., 2005). Mice were given wheel access for 8 weeks beginning at weaning. Additional mice (not shown) were housed without access to running wheels, and they showed no Selected (S) versus Control (C) difference in hematocrit. Thus, S mice are more responsive (more plastic) when granted wheel access, but not by virtue of a simple linear relation with amount of running that applies to all animals. Compare with Fig. 6B.