Occurrence of the myoid cell in the Harderian gland of the Japanese colubrid snake, Rhabdophis tigrinus.

An electron microscope study of the Harderian gland of the snake, Rhabdophis tigrinus, revealed the occurrence of a myoid cell in the glandular body. The myoid cell, in oval profile, is located in the perivascular space and enveloped by a basement membrane. The plasma membrane of the cell is studded with a number of vesicular caveoli. The myoid cell cytoplasm is largely occupied by myofilaments which do not form discrete bundles of myofibrils. The striations comprise the A and I bands together with Z lines, but neither an M nor an H zone is detectable. Although the transverse tubule appears to be scarce, the sarcoplasmic reticulum is well developed. No triadic configuration is observed. The cytoplasm includes a few numbers of mitochondria, sarcoplasmic reticulum, fat droplets, dense membrane-bound granules and free ribosomes. The histological characteristics of the present myoid cell are compared to those of identical cells commonly existing in the thymus.