Relationship Between the Tissue and Epimorphic Regeneration of Muscles

Entire muscles in vertebrate extremities can regenerate fromminced muscle fragments implanted into the bed of the removedmuscle. The histological course of regeneration of muscle fibersin this system is the same as that described in damaged mammalianmuscle. This type of regeneration has been called the tissueregeneration of muscle, and entire muscles have been regeneratedby this mode in urodelan and anuran amphibians, birds, and mammals.Entire muscles are also formed in a regenerating limb (an epimorphicregenerative process). It is postulated that there are two fundamentallydifferent modes of regeneration of muscles. Epimorphic regenerationis relatively slow, and the blastema seems to play an importantrole. The end product is morphologically and functionally perfect.Morphogenesis seems to be controlled in a manner analogous tothat in the embryonic limb. The tissue regeneration of musclesis rapid, occurring without the mediation of a blastema. Theend product is smaller and less well organized than a normalmuscle, and its morphogenesis seems to require the functionof the limb. A possible parallel reaction of skeletal elementsis discussed.