Fig. 7.

An ultrathin section of glutaraldehyde-osmium tetroxide fixed, araldite-embedded longitudinal section of a rabbit psoas muscle stretched to a length of 4.2 μm. It was stained with uranyl acetate, followed by lead citrate. The insert figure reveals the presence of ‘gap’ filaments between the ends of the myosin thick filaments (A) in the A band and the thin filaments in the I band. Labels: “A” is the A band; “I” is the I band; “Z” is the Z disc; “G” indicates the position of fine ‘gap’ filaments that are better resolved in the insert