CHANGES IN THE EPIDERMAL HISTOLOGY DURING THE SLOUGHING CYCLE IN THE RAT SNAKE PTYAS KORROS SCHLEGEL, WITH CORRELATED OBSERVATIONS ON THE THYROID GLAND

¹ Department of Biology, Brooklyn College, New York 11210 and Department of Pathology, Massachusetts General Hospital, Boston 02114; Department of Biology, The Catholic University of America, Washington, D. C. 20017; and Department of Zoology, The University, Hull, Yorkshire, England, U. K.

1. Study of the epidermal histology throughout the sloughing cycle in the snake Ptyas korros revealed the existence of a well-defined mesos layer and showed that the -layer is completed in the immediate post-shedding resting-phase. These observations supplement previous histological studies of the snake epidermis and further substantiate the essential homology of the epidermal generation in these forms with similar units in lizards.

2. Thyroid weight is not correlated with follicular cell height nor with epidermal cell changes throughout the sloughing cycle.

3. Changes in follicular cell height, indicative of varying levels of gland activity can be correlated with epidermal changes. The shedding complex and the outermost portions of the new inner epidermal generation differentiate during a period of lowest thyroid gland activity: gland activity is highest around sloughing.

4. These results provide a possible explanation for previous experimental studies of thyroid-sloughing relations in snakes. The problem of the difference between snakes and lizards in this context is discussed.