Structural changes developing with rigor that facilitate bacterial invasion of muscle tissue.

Pre-rigor skeletal muscle fibres shrank in hypertonic and swelled in hypotonic fixative solutions, but the radial dimensions of post-rigor muscle fibres did not change with variations in the effective osmolalities of fixative solutions. Muscle fibres apparently undergo radial shrinkage during the development of rigor and, in so doing, can pull away from their surrounding endomysia. The resulting gaps between post-rigor muscle fibres and endomysia probably contain muscle cell cytoplasm. Bacteria penetrate muscle tissue via these gap regions.