ABSTRACT The cicatrisation in lizard tissues after cauterization of the stump in amputated tails has been compared to the cicatrisation of the limb after amputation. The stump is covered by an initial loose connective tissue that contains fibrin exudates. A dense connective outgrowth is later formed from the stump. Collagen fibrils, granulocytes, and macrophages are more common in the connective of the outgrowths than in the normal regenerative blastema. Inflammatory cells remain in cauterized tissues for a longer period (over 20 days post-trauma) than in the normal blastema. Among fibrin exudate numerous fibrocytes with extensive rough endoplasmic reticulum rapidly synthesize a banded type of collagen fibrils that turn the connective tissue into a scar. The regenerating spinal cord, pigment cells, and muscles are trapped in this scar and regeneration is blocked. Also in the limb stump, numerous leucocytes and macrophages are present among amputated tissues in conjunction with a lasting inflammatory condition. It is concluded that the permanence of inflammation in tissues of the tail stump after cauterization and in the limb after amputation determines the failure of tissue regeneration. The process of cicatrisation in lizards represents a model to analyze inflammation and scarring in homeotherm vertebrates.
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