Histochemical Observations of Succinic Dehydrogenase Activity in Facial Muscles of Mammalians

¹ Department of Oral Surgery, Osaka University Dental School, 32-Joancho, Kitaku, Osaka, Japan

A histochemical study was carried out on the succinic dehydrogenase activity of orbiculo-lip muscles ( mostly M. orbicularis oris) and orbiculo-ocular muscles ( mostly M. obicularis oculi) of adult rats, guinea pigs, rabbits, dogs, and cats under normal conditions.

Enzymatically, the muscle fibers were classified into three types, red muscle fibers with a high enzymatic activity and a small diameter, white muscle fibers with a low enzymatic activity and a large diameter, and medium fibers with an intermediate enzymatic activity and an intermediate diameter between red and white fibers.

In the subcutaneous region of the lip in the animals examined, the muscle fibers among the hair sheath consisted of many red muscle fibers and a few medium fibers.

Pilomotor muscles in the animals studied were composed of two types of muscle fibers, in the same number of red and medium fibers.

Orbiculo-lip muscles were generally rich in red and medium fibers and scanty in white fibers. The localization of three types of the muscle fibers slightly varied depending upon the three parts of the orbiculo-lip.

Orbiculo-ocular muscles consisted of three types of muscle fibers. There are no great differences of distribution of fiber types between the upper and the lower palpebrae.