ABSTRACT
The first detailed light microscropic observations on the developing sarcoplasmic reticulum and T tubules were made by Emilio Veratti (Veratti, 1902, 1961). In newborn mouse muscle disorderly arrays of fine anastomosing filaments were seen throughout the muscle fiber, frequently elongated in the direction of the longitudinal axis (Fig. 3.1). The staining was attributed to an “apparatus existing in the sarcoplasm”. Within a few days after birth, the filaments began to rearrange themselves into transverse and longitudinal elements, and in adult mouse the transverse reticulum assumed a precise localization relative to the cross striation of the sarcomere (Veratti, 1902, 1961). This was a remarkable achievement in view of the small dimensions of the structures that would put them at the limit of light microscopic resolution. With the use of the electron microscope the filaments of Veratti were resolved into two distinct networks of tubules and cisternae, that are arranged in a precise pattern with respect to the contractile proteins of the myofibrils (Fig. 3.2) (Porter, 1956, 1961; Porter and Palade, 1957; Peachey and FranziniArmstrong, 1983; Franzini-Armstrong, 1994; Franzini-Armstrong and Jorgensen, 1994).
