The "forgotten zone": acquired disorders of the trachea in adults.

The upper airway is generally defined as the air passage segment that extends between the naso- or oropharynx and the carina. The longest segment of the upper airway-the trachea-begins at the inferior portion of the larynx and extends to the branch point of the main carina. The trachea has the potential to be a "forgotten zone" in differential diagnoses, as pathological processes involving this portion may not receive prominent clinical consideration in disorders presenting with respiratory symptoms and signs. Unlike the oropharynx, this anatomical area is beyond visualization on routine inspection; unlike the mediastinum and lung fields, it is a potential "blind spot" on initial, plain radiographic examination of the chest. Nonetheless, the adult trachea is affected by a number of primary disorders and is also a target organ of a variety of systemic diseases. This review will focus on both primary and systemic diseases involving the adult trachea with specific attention to their clinical manifestations and diagnostic hallmarks.

The discovery of viruses: advancing science and medicine by challenging dogma.

The discovery of viruses in the final years of the nineteenth century represented the culmination of two decades of work on tobacco mosaic disease by three botanical scientists. Eventually their discovery led to a paradigm shift in scientific thought, but it took more than 20 years to appreciate its implications because it was inconsistent with the prevailing dogma of the time-Koch's postulates. Although these 'rules' were actually conceived of as guidelines upon which to establish microbial causality and their implementation resulted in many new discoveries, they also had the unintended effect of limiting the interpretation of novel findings. However, by challenging existing dogma through rigorous scientific observation and sheer persistence, the investigators advanced medicine and heralded new areas of discovery.