Intracellular impulse conduction in muscle cells.

A hypothesis, suggested previously by morphological studies, for impulse conduction from the sarcolemma to the contractile material via the sarcoplasmic reticulum is discussed. The relation of reticulum morphology and cell size to speed of contraction in smooth and striated muscle agrees with the hypothesis and thus supports it. Additional support comes from evidence concerning an unusual morphological relationship between the sarcolemma and contractile fibrils in striated muscle of amphioxus.