The subdermal glands of Hippopotamus amphibius are scattered over almost the entire skin surface, but are most frequent over the dorsal and flank skin. They are situated in the plane between the dermis and the subcutaneous tissue. They are from 2–5 cm. to 0–5 cm. in diameter, lenticular in form, and usually possess two secretory ducts.
Histologically, they are compound tubulo-acinar glands. The acini are composed of varying proportions of mucous cells and granular serous cells. The tubular system of secretory cells opens into a collecting system of larger ducts, which in turn open into the main secretory duct, which spirals through the thick collagenous dermis to end at a punctum on the epidermal surface.
The communications of Tomes (1850) and Crisp (1867) to the Society are quoted, and the relationship between the observable phases of secretion and the various types of secretory cell is described.