i 594 HUMAN ANATOMY. 



lingual nerve. The relation of that nerve to the floor of the mouth posteriorly 

 has already been described ( page 1249). 



The fold of mucous membrane constituting the frenum may be abnormally 

 short and prevent the free movements of the tongue, interfering with sucking during 

 infancy and with articulation later. When its division is necessary, it should be cut 

 through close to the jaw, and with blunt-pointed scissors directed away from the 

 tongue so as to avoid the ranine veins which may be seen close to it on the under 

 surlace of the tongue. 



The ranine arteries lie farther out and are more deeply situated, being placed 

 beneath two converging raised fringed lines of mucous membrane, the plica 

 flmbriatte. 



A sublingual bursa is described by Tillaux as a triangular space situated between 

 the genio-hyo-glossus and the mucous membrane, its tip being at the frenum, its 

 base at the sublingual gland. Its existence, by no means constant, is said by Tillaux 

 to explain the occurrence of the acute cystic tumor (grenouillette} , " acute ranula,' 7 

 which is occasionally met with in this region. 



Ranulae ordinary retention cysts are common in the floor of the mouth, and 

 branchiogenic cysts, due to the incomplete closure of the first branchial cleft, are 

 sometimes found there. 



The Cheeks. The buccal limits of the cheeks are accurately indicated by the 

 reflections of mucous membrane lining them. By making outward traction on the 

 angle of the mouth that membrane can be seen and palpated, and ulceration, as 

 from a jagged tooth or beginning epithelioma, or mucous patches, or abscess, or new 

 growths, can easily be detected. 



The papilla indicating the opening of the parotid duct may be seen or felt 

 opposite the upper second molar tooth. A fine probe may be made to enter 

 the duct for a short distance, the normal curves then interfering with its passage 

 (Fig. 1343). 



Lipoma originating in the "boule de Bichat" (page 493) can be recognized. 



As the jaws are separated and closed the anterior border of the masseter may 

 be seen and felt. The important structures of the cheek the facial vein and artery 

 and the parotid duct are all anterior to this line (Fig. 691). 



The Tongue. Congenital deformity of the tongue is rare. Forked tongue 

 normal in some birds and reptiles and in seals is rare ; it is usually in asso- 

 ciation with other developmental defects, as cleft palate. Congenital absence has 

 been noted (de Jussieu). 



Macroglossia {lymphangioma cavernosum, Virchow) is a congenital affection 

 in which the lymph-channels and lymph-spaces are dilated and the lymphoid tissue 

 throughout the tongue, but especially at the base, greatly increased. The tongue 

 may attain an enorntous size, and has even, by pressure, caused deformities of the 

 teeth and alveolar arches and luxation of the mandible. The foramen caecum, indi- 

 cating the junction of tin- pharyngeal and buccal parts of the tongue, is the superior 

 termination of the fcetal thyro-glossal duct. " Ducts lined with epithelium have been 

 found leading from the foramen caecum to accessory glands about the hyoid bone. 

 It is probably from these glandular and epithelial collections about the hyoid bone 

 that crrtain deep-seated forms of cancer of the neck are developed. Some of these 

 take th- form of malignant < ysts" ( Treves). 



The upper surface of the tongue lias for centuries been the object of especial 

 observation in disease. The practical value of these observations is not univer- 

 sal! v conceded, and too much weight has been placed upon them ; but there can 

 be no doubt that some help in prognosis and even in diagnosis in digestive de- 

 rangements, in fevers, and in various toxaemias may be obtained by inspection of 



tile tiillglle. 



The " fur," so carefully studied, consists of a mixture of d-esquamated epithelial 

 cells, food particles, and micro < .rganisms of various kinds overlying living epithelium 

 which mav be abnormally proliferating. 



The surface between the circumvallate papilla- is apt to be the most heavily 

 coated, either in health or disease, because it is the least mobile part of the tongue 

 and is not kept .lean by f.i.-tion, as are the sides and tip. The appearance of 



