Observations on the microcirculation in the gingiva of hamsters and other laboratory animals.

By using the teeth for immobilisation and employing incident light microscopy at magnifications up to 240 X, entire capillary beds could be observed in the labial gingiva in small laboratory animals. In the mandibular incisor region, simple capillary loops, as found in the human gingiva and nail bed, were absent in all species examined except in some guinea pigs. In the hamster, where the topography of the gingival capillary bed was studied in greatest detail, blood flow was regulated by changes in caliber of arterioles; by opening and closing of exits from main capillary channels into networks apparently devoid of vasomotor activity; and by opening and closing of arteriovenous anastomoses. Under certain conditions, settling of blood cells and blood cell clumps to the lower side of gingival veins, together with gravitationally layered flow, was observed.