The pancreas is composed of acini lined with columnar cells; between the acini are small groups of cells termed interalveolar cell islets (islands of Langerhans). There are two main types of cells in the islands of Langerhans, distinguished as alpha and beta cells, according to special staining reactions of the granules which they contain. The functions of the acinar cells and of the beta cells of the islands of Langerhans are comparatively well defined and progress is being made in the study of the functions of the alpha cells. Tests whereby the functions of each type of cell may be studied will be reviewed, and the clinical use of such tests will be described.
TESTS FOR DISTURBANCES OF EXTERNAL SECRETION OF ACINAR CELLS
The external secretion of the acinar cells is carried by the pancreatic duct to the duodenum. This secretion is under the control of both nervous (vagal) and