THE ORGANS OF DIGESTION 



like invagination occurs, to form the middle thyroid rudiment, and this depression is represented 

 in the adult by the foramen cccum of the tongue. In the adult the union of the anterior and pos- 

 terior parts of the tongue is marked by a V-shaped depression (sulcus terminal is), the apex of 

 which is at the foramen cecum, while the two limbs run outward and forward, parallel to, but a 

 little behind, the circumvallate papillae. The prominent anterior part of the furcula forms the 

 epiglottis; the furrow behind it is the entrance to the larynx; and the anterior parts of its lateral 

 margins constitute the arytenoepiglottidean folds. 



Tuberculum impar 

 (papillary part of tongue). 



Posterior part of tongue. 



Furcula. 



Entrance to larynx, 



Mandibular arch. 



Hyoid arch. 



Third arch. 

 Fourth arch. 



-Lung. 



FIG. 944. The floor of the pharynx of a human embryo about twenty-three days old. X 30. (From His.) 



Applied Anatomy. The diseases to which the tongue is liable are numerous, and its ap- 

 plied anatomy is of importance, since any or all the structures of which it is composed muscles, 

 connective tissue, mucous membrane, glands, vessels, nerves, and lymphatics may be the seat 

 of morbid changes. It is not often the seat of congenital defects, though a few cases of vertical 

 deft have been recorded, and it is occasionally, though much more rarely than is commonly sup- 

 posed, the seat of tongue-tie, from shortness of the frenum. 



There is, however, one condition which must be regarded as congenital, though not uncom- 

 monly it does not exhibit the significant changes until a year or two after birth. This is an 

 enlargement of the tongue which is due primarily to a dilatation of the lymph channels and a 

 greatly increased development of the lymphatic tissue throughout the tongue (macroglo.tsici). This 

 is often aggravated by inflammatory changes induced by injury or exposure, and the tongue may 



Papillary portion of tongue. 



Mandibular arch. 



Hyoid arch. 



Foramen caecum. Posterior part Third arch. 



of tongue. 

 FIG. 945. Floor of mouth of an embryo slightly older than that shown in Fig. 944. 



X 16. (From His.) 



assume enormous dimensions and hang out of the mouth, giving the child an imbecile expression. 

 The treatment consists in excising a V-shaped portion and bringing the cut surfaces together 

 with deeply placed silver sutures. Acute inflammation of the tongue (acute glossitis) may 

 be caused by injury or the introduction of some septic or irritating matter, and it is attended 

 by great swelling from infiltration of the connective tissue of the tongue; this connective tissue 

 is present in considerable quantity. The great swelling renders the patient incapable of swal- 

 lowing or speaking, and may seriously impede respiration. The condition may eventuate in 

 suppuration and the formation of an acute abscess. Chronic abscess, which has been mistaken 

 for cancer, may also occur in the substance of the tongue. 



The mucous membrane of the tongue may become chronically inflamed, and presents different 

 appearances in different stages of the disease, to which the terms leukoplakia, psoriasis, and 

 ichthyosis have been given. 



