[The salivary glands within the history of physiology].

In the rapid development of physiology during the second half of the 19th century the salivary glands played a remarkable part. Numerous of the famous physiologists of that age used these glands in experiments, which yielded new knowledge of far-reaching importance, particularly to neurophysiology. Nerves with hitherto unknown functions were found when Carl Ludwig discovered the secretory nerves and Claude Bernard the vasodilator nerves in experiments on the submaxillary gland. Motor nerves to myoepithelial cells were first observed in parotid glands. The conception of an "autonomic nervous system", composed of a parasympathetic and a sympathetic part, was created by Langley after observations, inspired by decades of work on salivary glands. Pavlov based the idea of the "conditioned reflexes", through which he studied the function of the cerebral cortex, mainly on experiments on salivary glands. Present research on nonadrenergic non-cholinergic transmission of nerve impulses has its origin in Heidenhain's observations on the action of atropine on salivary glands. The understanding of the secretory process in general was also promoted in these early experiments on salivation. Results from simultaneous measurements of the pressure in the sallivary duct and the arterial system, carried out by Ludwig, excluded the then current hypothesis that saliva is formed by filtration of the blood. Barcroft demonstrated that activity in salivary glands is accompanied by increased consumption of oxygen and formation of carbon dioxide. The salivary glands have also attracted physiologists in more recent years. For instance, the first observations on the electrical events on the cellular level in glands were made in submaxillaries; and the first normal tissue in which the presence of the nerve growth factor was found, was the submaxillary gland of the mouse.