Figure 2. Halothane sensitivities in human type 1 and 2 skinned masseter and vastus lateralis fibers. The halothane concentration that induced 10% of the maximal contracture with pCa 4.8 solution (pCa =-log Ca++concentration) is shown in panel A for each masseter muscle fiber (circle) and in panel B for each vastus lateralis fiber (square). Closed symbol = type 1 fiber; open symbol = type 2 fiber. There was a significant difference in halothane sensitivity (P < 0.001) between type 1 masseter muscle fiber (0.6 +/− 0.2 vol%) compared with type 1 or type 2 vastus lateralis fibers. There was no significant difference in halothane sensitivity between type 1 (2.7 +/− 0.6 vol%) and type 2 (2.5 +/− 0.4 vol%) vastus lateralis fibers.