The sarcomere length--isometric tension diagram of the toad Bufo bufo sartorius

The sarcomere length--isometric tension diagram has been determined for the toad Bufo bufo sartorius using a laser diffraction technique to measure the sarcomere width. The sarcomere width at l0 was found to be 2.37 micron. At length shorter than l0 this whole muscle exhibits a steeper decline in tension than single fibres. This discrepancy in the shape of the tension-length diagram between single frog fibres and whole toad sartorii may be due to a difference in the magnitude of the internal force which appears only at short lengths.