Histological studies on the parathyroid glands of lizards

1. Number, position, size, shape, and vascular bed of the parathyroid glands of Chalcides ocellatus and Scincus scincus are described. The collagenous capsule is pigmented in Chalcides and pigment-free in Scincus. The internal “capillary” network is more developed than the subcapsular. 2. Seasonal changes in the activity of the glands are noticed. From April to October, the glands are active having a compact appearance. In the remaining months, “foraminated”, i.e., partially active glands are found. The glandular tissue can rearrange itself according to the degree of activity, either in the form of rounded lobules or cellular cords. In winter, degeneration takes place and nearly half of the parathyroid tissue is destroyed. In Chalcides, this occurs in the centre of the gland while the rest of the cells show limited activity, because the animal is a non-hibernator. In Scincus, mostly the peripheral part degenerates while the rest of the gland appears foraminated, because the animal is a hibernator. The rebuilding of the glandular tissue presumably takes place by amitosis. Partial destruction of the parathyroid may be caused also during summer by starvation. 3. Large acini are rare in the parathyroid gland of Chalcides but are very frequent in that of Scincus. Their size differs greatly and their condition may indicate the degree of activity of the gland. Their presence might represent a phase of storage of the parathormone, or the colloid of the acini may be inert. 4. Glands of Chalcides individuals subjected for a long time to high temperature are large and show abnormally high concentrations of nuclei. Some of the glands show also degeneration in the centre.