[Histochemical and morphometric characteristics of some extraocular muscles of the dog]

This investigation was carried out on retractor bulbi, lateral and medial rectus muscles of six adult dogs. Tissues were collected from near the center of individual muscle bellies. These were stained for m-ATPase at varying pHs during preincubation, NADH-TR, Alpha-GPDH, Modified Mason trichrome and Hematoxyline and Eosin. Muscle fibers were classified as type I and type II, based on their reaction for m-ATPase. The retractor bulbi muscle was composed entirely of type II, oxidative, muscle fibers, with no glycolytic fibers. The rectus muscles presented a stratified composition, with superficial muscle fiber bundles containing a mixture of type II fibers oxidative and glycolytic, and central bundles of type I, mixed with type II. It was observed that there was less interstitial tissue in the center of the muscle bellies. Large diameter nerve fibers were also observed in the central layers.