COMPARATIVE ANATOMICAL AND NEUROHISTOLOGICAL OBSERVATIONS ON THE TONGUE OF THE MARSUPIALS.

Abstract

AbstractMacroscopic and neurohistological observations of the red, gray and tree kangaroo and wombat's tongues are described. On the dorsum, three circumvallate papillae, foliate papillae (gland‐duct type), fungiform papillae and filiform papillae are observed. In the wombat, the vallate papillae are shaped like a “lotusnut.” Its summit is broadened, rough, and reaches the level of the dorsal surface. The papillae of the kangaroo are shaped like a “walnut” and are situated below the dorsal surface of the tongue. The vallate papilla is occupied with abundant nerves, thin non‐myelinated and thick myelinated fibers, and ganglion cells, multipolar and unipolar. In the upper area of the wombat's papilla, however, there is a demarcated thin layer of non‐innervated connective tissue. Therefore, taste buds are located in nearly the whole wall of the papilla in the kangaroo, but only in the lateral wall in the wombat, closely associated with the subgemmal nerve plexus. Foliate papillae of gland‐duct type, which connect with the serous glands, have many taste buds innervated with thin fibers from the periductal nerve plexus. Also in this region there are many ganglion cells. This gland‐duct type may be regarded as the primitive form of the common foliate and vallate papillae; i.e., foliate papillae may be developed from a linear gathering of its anlages, vallate ones from a circular gathering and bellshaped vallate form from an atypical type of the circular gathering. Taste buds may serve as a chemoreceptor for gland secretion in the tongue because their position does not exhibit any suitable form to receive the sense of taste. Richly innervated fungiform papillae contain a few taste buds, but poorly innervated ones have none in the upper epithelium. Filiform papillae are of a vascular nature. In the apical region of the tongue Vater‐Pacinian corpuscles of simple type are found.