Historical Note on the Capillaries, with Citations from an Early American Text

2nd Century, A.D.: Galen postulated arterio-venous anastomosis. 1628: Harvey demonstrated the circulation of the blood. 1661: Malpighi saw capillaries in the lungs and in the webs of living frogs. 1667: Leeuwenhoek observed the web of the flying squirrel. 1733: Hales determined arterial blood pressure. From calculations on perfusion experiments he made deductions regarding the number of capillaries, the rate of flow, and pressure in the capillaries. 1729-99: Spallanzani discovered the white blood cells. 1728-93: Hunter, from clinical observations, deduced that in inflammation there is more blood in a certain part due to the opening up of vessels which previously did not admit red blood. 1756: Haller denied the independent action of the capillaries. 1785: Vacca described fat and lymph capillaries, i.e., capillaries not containing blood cells. These were also called serous capillaries. 1785: Hewson described the plasma. 1804: Philip discussed, from experimental evidence on intact living mammals, the independent activity of capillaries in inflammatory processes. 1836: Shulz observed the dilatation and contraction of the capillaries. 1858: Lister thought the changes observed in capillary diameter were passive and due to a rise of arterial pressure. 1865: Stricker noted the independent contraction and dilatation of the capillaries in the excised nictitating membrane of the frog. 1865: Virchow identified leukocytes in pus. 1876: Cohnheim described diapedesis in frogs. 1873: Rouget observed the independent contraction of the capillaries in the tadpole, and described the cells which bear his name.