electron microscope examinations of purkinje fibers from the septa , papillaries , trabeculae carneae and small endocardial strands from chicken , sheep , dog and monkey hearts have revealed a close association between densely stained striations of supernumerary z line material and successive parallel tubules in the network formed by the sarcoplasmic reticulum ( sr ) .
C0014124
endocardial
C0018787
hearts