The microcirculation of the pancreas in the anaesthetized rabbit was examined by in vivo microscopy and micro-cinephotography. 2. The islets of Langerhans were identified by their appearance following the systemic injection of diphenylthiocarbazone. 3. Arterial injection of Evans blue demonstrated the arrangement of vessels within the pancreas. Blood leaving the islets passed via capillaries into the capillary meshwork; no islet was ever seen to be drained directly by a vein. 4. This significance of this portal arrangement is discussed.
