The Fine Structure of Myo-tendon Junction in Some Mammalian Skeletal Muscles.

The mode in which the force exerted by the contraction of myofibrils is transmitted to tendon has been debated for many years (as reviews HAGGQVIST 1931 and 1956). It is generally accepted that the major union of muscle with tendon is established at the end of muscle fibers. Light-microscopically, two main opposing theories appear in the literature regarding the muscle-tendon attachment. One is continuity theory, which maintains that myofibrils are directly continuous with tendon fibrils. The other is sarcolemma theory, which holds that the sarcolemma forms a limiting membrane between myofibrils and tendon fibrils. In recent years, the sarcolemma theory has been strongly supported by several investigators using the silver impregnation method (GOSS 1944 and LONG 1947). The final solution of this problem, however, has been achieved by the application of electron microscopy. Since PORTER (1954) made a electron microscopic observation on the myo-tendon junction in larval forms of Amblystoma punctatum, many investigators (RUSKA 1954, BENNETT 1955, EDWARDS et al. 1956, COUTEAUX 1957 and 1959, SCHWARZACHER 1960, GELBER et al. 1960, MUIR 1961) have studied this subject by the aid of electron microscope. GELBER et al. (1960) have presented a three-dimensional scheme of the myo-tendon junction. Thus they all have confirmed, supporting the sarcolemma theory, that the end of a muscle fiber forms complex processes or indentations and is enveloped by a continuous sarcolemma. However, there are still some differences of opinion in the literature. The present investigation has dealt with the myo-tendon junction in some mammalian skeletal muscles with the recently improved preparation techniques in electron microscopy.