LUDWIG, KARL FRIEDRICH WILHELM (1816 1895), German physiologist, was born at Witzenhausen, near Cassel, on Dec. 29, 1816. He studied medicine at Erlangen and at Marburg, where he taught anatomy and physiology until 1849. He then became professor at Zurich. In 1855 he went to Vienna in the same capacity and ten years later was appointed to the newly created chair of physiology at Leipzig. By the new appa ratus and methods that he introduced into the service of physi ology, Ludwig exercised a great influence on the progress of that science. He adapted the kymograph invented by Thomas Young for the obtaining of a written record of the variations in arterial pressure and of the movements of respiration. For his researches on the gases in the blood he designed the mercurial blood-pump, which also aided him in his work on the gases of the lymph, the gaseous interchanges in living muscle, the significance of oxidized material in the blood, etc. In regard to secretion, he showed that
the secretory glands, such as the submaxillary, are more than mere filters, and that their secretory action is attended by chem ical and thermal changes both in themselves and in the blood passing through them. He demonstrated the existence of a new class of secretory nerves that control this action, and showed that if the nerves are appropriately stimulated the salivary glands continue to secrete, even though the animal be decapitated. This was but one phase of his rejection of the assumption of the vital ist that the phenomena of life depend on laws and forces different from those operating in inorganic nature, a rejection which was expressed in his celebrated Text-book of Human Physiology (1852-56).