Abstract
There are three kinds of muscle fibres in function such as twitch fibre, slow fibre and intrafusal fibre, in the frog's skeletal muscle. The electric characteristics of twitch fibre were detailed by Fatt and Katz (1), and the junctional potential and the innervation in slow fibre were investigated by Kuffler and Vaughan (2, 3), moreover the characteristics and the innervation of intrafusal fibre being clarified by Koketsu and Nishi (4, 5). These three fibres different in their appearence may be due to difference of membrane resistance, fibre radius, length constant, membrane time constant, or effective resistance. When the focal potential, in other words a maximal potential at junctional region, initiated by motor nerve stimulation, was intracellularly recorded, the difference in decaying time or in decaying curve was observed in these fibres (Fig. 1). The author analysed these differences from the point of view of temporal change of permeability and number of junction.
