Electron Microscopic Studies of the Follicle Cells

The thyroid gland holds a unique situation among the endocrine glands. The follicle cells line the follicle cavity by their apical surface and have an intimate relation with the capillaries at their basal surface. Until recently, attention has been paid to the problem of function involved in this arrangement by light microscopy. Hormone substance secreted into the follicle cavity and stored here is held in readiness to be resorbed by the follicle cells and later transported basally to be discharged into the circulation. Today, interest in the process of secretion and transport has been aroused by repeated electron microscopic studies, and the present study was undertaken, using the thyroid glands of dogs, with the object of filling the gaps in knowledge and presenting some new evidence.