The ultrastructure of the capsule of the neuromuscular spindles from Python reticulatus (Schneid.).

The capsule of the neuromuscular spindles in the lower costocutaneous muscles from Python reticulatus (Schneid.) has been studied at the electron microscope. As in other vertebrate species, the capsule is divisible into 2 components, i.e. an inner and an outer capsule, which display a very similar structure. Moreover, it has been possible to bring to light the continuity of the outer capsule with the cells and fibres of the perineural sheath enveloping the sensory and motory fibres. The capsule cells exhibit a number of pinocytotic vesicles, profiles of granular endoplasmic reticulum, mitochondria, glycogen particles and Golgi complexes. The presence of these structures points to the secretory and transport activities performed by the spindle capsule in the control of the composition of the intracapsular fluid.