A study of the membrane constants in the dog myocardium.

WEIDMANN19) used cable analysis to obtain the membrane constants of the false tendon of the kid heart. Attempts to apply the cable theory have also been made on the terminal Purkinje fiber of the dog heart and an equivalent linear cable consisting of several component fibers attached side by side was analyzed by MATSUDA9). Experimental verification of the cable theory on the regular cardiac muscle, however, seems to be extremely difficult because of the complicated syncycium-like structure of the myocardial fibers. WOODBURY et al.21) proposed a planar model for the rat atrium, and TANAKA et al.15), a lattice model for the mouse ventricle. Both groups showed theoretically and experimentally that the extremely rapid spatial decline of a tonically applied potential can be expressed by a Bessel function. Thus, it seems strange that conduction of excitation in the ordinary cardiac muscle is known to occur with a high safety factor which is almost comparable to that of nerve and skeletal muscle fibers13,17,20). These facts strongly suggest that a group of myocardial fibers works as a functional bundle as just pointed out in the mammalian smooth muscle16). KAMIYAMA and MATSUDA7), to circumvent these complexities in fiber structure, utilized a partition chamber method for polarizing the ventricularmuscle fibers and showed that in these circumstances aggregates of muscle fibers could be regarded to behave as a one-dimensional cable. We used this