As the mouth is exposed in a special manner to external influences, its mucous membrane possesses an epithelium in many layers, and it is not nearly so liable to inflammations as are most other parts of the alimentary canal. It is to be noted that even extensive wounds of the mouth do not commonly take on a septic character, as if the rich epithelium had the power of neutralizing influences of that sort. .
Malformations of the mouth are represented by Cleft-palate and Hare-lip, which have been already referred to at p. 52.
Atrophy of the tongue is a regular result of bulbar paralysis when the nucleus of the hypoglossus has been involved, as is usually the case. Hemiatrophy is a much more rare lesion. It occurs for the most part in consequence of interference with the hypoglossal nerve in its course by wounds, tumours, disease of bone, etc. It has also been observed in cases of locomotor ataxia in which there may be a lesion of the nucleus of the hypoglossal nerve.
Amyloid degeneration is not very uncommon affecting the vessels. It has been observed in the form of nodular tumour-like masses. The muscular and glandular tissue undergo atrophy in the affected regions. Fatty infiltration of the tongue is not infrequent in emaciating diseases.
Erb, (with literature) Deutsch. Arch. f. klin. Med., xxxvii., 1885; Raymond et Artaud, (atrophy in tabes) Arch, de Physiol, norm, et path., 1884; Ziegler, (amyloid disease) Virch. Arch., 65, 1875.