Figure 2

Immunohistochemical labelling of representative serial cross-sections of the quadratus plantae lateral head. Top: Muscle fibers labelled for Type II (fast) myosin heavy chains with antibody A4.74 (positive labelling appears as dark staining). Bottom: Muscle fibers labelled for Type I (slow) myosin heavy chains with antibody A4.951. Single asterisk indicates a fiber classified as Type II, demonstrated by positive labelling in A and absence of labelling in B. Double asterisk indicates a fiber classified as Type I, demonstrated by positive labelling in B and absence of labelling in A. Insets: Cross-section of a different individual exhibiting a hybrid fiber (star), classified based on positive labelling by both antibodies. In both individuals muscle tissue exhibits grouping of fibers into patches of similar types. Scale bar: 50 microns.