Figure 2.

Ca²⁺- and Sr²⁺-activation profiles of diaphragm fibers from fetal newborn and adult sheep. Zero minutes (Term) fibers were taken from fetuses where the ewe was in labor at 147 days gestation, but no breathing had occurred and the lungs remained filled with fluid. Eight hours (Postnatal) refers to a lamb that had been delivered and allowed to auto-resuscitate and breathe for 8 h until autopsy. Note the change of the force–pSr relationship from fetal to postnatal life; full description is given in Section “Results.”