text: Early studies of airway submucosal glands.
  This historical article provides a comprehensive review of early research on the structure and function of airway submucosal glands. The literature before 1950 or so, is virtually unknown, but in addition to being of historical interest it contains much of relevance to current research. Airway glands were first mentioned in 1602. The first description of their general form, size, and distribution was in 1712. Gland morphology was determined in 1827 by injecting mercury into their openings. Wax was later used. Detailed comparative information for all regions of the tracheobronchial tree was provided by Frankenhauser in 1879 (Untersuchungen uber den bau der Tracheo-Bronchial-Schleimhaut). Histological studies began in 1870, and by the end of the 19th century, all the major histological features had been described. The first physiological studies on airway mucous secretion were published in 1892. Kokin, in 1896 (Archiv für die gesamte Physiologie des Menschen und der Tiere 63: 622-630), was the first to measure secretion from individual glands. It was not, however, until 1933 that gland secretion was quantified. This early literature raises important questions as to the role of the collecting duct epithelium in modifying primary secretions. It also provides perhaps the most accurate measure of basal gland secretion in vivo.