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  • Updated 10.17.2022
  • Released 10.17.2022
  • Expires For CME 10.17.2025

Disorders of gustation

Introduction

Historical note and terminology

Galen (129-201 CE) correctly described the different functions of the three principal nerves supplying the tongue (lingual, glossopharyngeal, and hypoglossal nerves) and demonstrated their origin at the base of the brain (177).

Printed medical illustrations began in 1490 and, by the beginning of the 16th century, included representations of afferent connections from the special sensory organs to the brain (97). These were typically part of highly schematic diagrams of brain function representing the medieval cell doctrine, in which usually three “cells” or ventricles were assigned functions of sensory integration and imagination, cognition, and memory (98). Indeed, many early-16th-century woodcuts of the medieval cell doctrine show presumptive connections between the organs subserving the special senses, either with the most anterior cell or ventricle of the brain or with a specific portion of it--the sensus communis (ie, sensory commune, or common sense, a structure Aristotle had postulated is responsible for monitoring and integrating the panoply of sensations from which unified conscious experience arises) (97; 98; 99). A representation of the tongue and presumptive pathways to the brain are incorporated into many of these woodcuts (99; 99). These stereotyped 16th-century schematic images typically linked the tongue to an anterior cell or a portion of it. Such images linked the gustation via the tongue to "cells" of "ventricles" before the advent of more realistic images and schematics began to show the neural gustatory pathways beginning in the mid-sixteenth century.

Observational anatomy was largely lost from the time of Galen in the second century, and it became regimented and dogmatized with the scholasticism of the Middle Ages until a few anatomists began to seriously challenge Galen beginning in the 16th century. Most notably, Flemish anatomist Andreas Vesalius (1514-1564) provided much greater realism with the publication of his de Humani corporis fabrica (1543).

Vesalius depicted dissection of the face, isolating the tongue, as part of one of his elaborate depictions of the famous “musclemen.”

Vesalius also separately made a schematic of the cranial nerves, including innervation of the tongue, but the pathway for taste sensation had not been determined by this point.

Even after Vesalius championed a return to observational anatomy, the medieval cell doctrine and its associated representation of the olfactory pathways persisted well into the 19th century, even if it was gradually moved to the fringes of medical thought (99).

By the 18th century, anatomists were working to realistically represent anatomical structures, as epitomized by the copperplate engravings of Dutch Golden Age physician, anatomist, poet, and playwright Govert Bidloo or Govard Bidloo (1649-1713).

This continued into the 19th century, with amazingly realistic and detailed colored lithographs, including the outstanding examples of Irish-born English anatomist Richard Quain (1800-1887) and German anatomist Christian Wilhelm Braune (1831-1892) in his topographical anatomy atlas (1867-1872).

The structure of the tongue surface was first described in 1609 by Italian anatomist Giulio Cesare Casseri (1552-1616) and then in 1665 by Italian physician-anatomist Lorenzo Bellini (1643-1704), who published the observations made by Italian biologist, physician, and pioneering microscopist Marcello Malpighi (1628-1694) the previous year (82; 177). After the discovery of taste buds in fishes by German zoologist and comparative anatomist Franz von Leydig (1821-1908) in 1851, German anatomist and zoologist Franz Eilhard Schulze (1840-1921) suggested in 1863 that they were chemosensory structures. Nineteenth-century studies focused on cytologic features and nerve supply.