The Collaborative International Dictionary
Perimysium \Per`i*my"si*um\, n. [NL., fr. Gr. ? about + ? muscle.] (Anat.) The connective tissue sheath which surrounds a muscle, and sends partitions inwards between the bundles of muscular fibers.
Wiktionary
n. A layer of connective tissue which surrounds several muscle fibers into bundles.
Wikipedia
Perimysium is a sheath of connective tissue that groups muscle fibers into bundles (anywhere between 10 and 100 or more) or fascicles.
Recent advances in muscle physiology suggest that the perimysium plays a role in transmitting lateral contractile movements. This hypothesis is strongly supported in one exhibition of the existence of "Perimysial Junctional Plates" in ungulate Flexor carpi radialis muscles constructed by E Passerieux. The overall comprehensive organization of the perimysium collagen network, as well as its continuity and disparateness, however, have still not been observed and described thoroughly everywhere within the muscle.
Usage examples of "perimysium".
By uniting with the bone at one end and blending with the perimysium and fiber bundles at the other, the tendon forms a very secure attachment for the muscle.