Section 60. The lining of glands is secretory epithelium; the cells are usually cubical or polygonal (8, g.ep.), and they display in the most characteristic form what is called metabolism. Anaboly (see Section 14) we have defined, as a chemical change in an upward direction-- less stable and more complex compounds are built up in the processes of vegetable and animal activity towards protoplasm; kataboly is a chemical running down; metaboly is a more general term, covering all vital chemical changes. The products of the action of a glandular epithelium are metabolic products, material derived from the blood is worked, up within the cell, not necessarily with conspicuous gain or loss of energy, and discharged into the gland space. The most striking case of this action is in the "goblet cells" that are found among the villi; these are simply glands of one cell, unicellular glands, and in Figure V. we see three stages in their action: at g.c.1 material (secretion) is seen forming in the cell, at g.c.2 it approaches the outer border, and at g.c.3 it has been discharged, leaving a hollowed cell. Usually however, the escape of secreted matter is not so conspicuous, and the gland-cells are collected as the lining of pits, simple, as in the gastric, pyloric, and Lieberkuhnian glands (Figure VIII., Sections 23, 29), or branching like a tree or a bunch of grapes (Figure r.g.), as in Brunner's glands (Section 29) the pancreas, and the salivary glands. The salivary glands, we may mention, are a pair internal to the posterior ventral angle of the jaw, the sub-maxillary; a pair anterior to these, the sub-lingual; a pair posterior to the jaw beneath the ear, the parotid, and a pair beneath the eye, the infra orbital.