204 SPECIAL ANATOMY. 



sometimes the first molar, rarely the external incisor teeth, remain unde- 

 veloped. Occasionally some molar teeth exceed the number (more frequently 

 in Negroes). With many children the eruption of the milk teeth takes place 

 before birth. A third mutation sometimes occurs with the posterior molar 

 and the incisor teeth. 



434. 5. The Pharynx, 



a funnel-shaped muscular semi-canal behind the nasal and oral 

 cavities and the larynx, in the central line before the five superior 

 cervical vertebrae, at the superior part called the fauces, is closed 

 above, behind and at the sides, but before and below (where it 

 passes into the cesophagus) open. Narrower than the mouth, but 

 wider than the oesophagus, its breadth measures above (between 

 the posterior borders of the internal wings of the P. pterygoidei) 

 about one inch, farther down (between the posterior extremities 

 of the alveoli) two inches [during contraction of the muscles only 

 one inch], still deeper (between the inferior cornua of the thyroid 

 cartilage; rather above one inch [to almost complete closure 

 during contraction of the muscles]. Length : four to four and a 

 half inches [may be elongated to about five and a half, shortened 

 to two and a half inches]. 



The external surface is formed of a muscular coat, behind, 

 united with the fascia cervicalis (profunda) by loose uniting tis- 

 sue, and is situated before mm. recli capit. antic., and longus 

 colli; is at the sides separated from m. pterygoideus intern, by 

 a triangular (below broad) space, in which are found: Carotis 

 interna, F. jugular, intern., Nn. vagus, glosso-pharyng., hypo- 

 glossus, accessor. Willis., farther down many lymphatic glands 

 and Carotis externa. Above (the roof) it is attached to the pars 

 basilar. ossis occipitis. 



The internal surface is covered with mucous membrane. The 

 anterior wall is wanting; instead, we see: 1. The two posterior 

 nasal openings. 2. The superior surface of velum palatinum, 

 above which the fluid from the nose flows into the posterior part 

 of the mouth. 3. The semicircular isthmus faucium. 4. The 

 superior opening of the larynx closed by the epiglottis. 5. The 

 posterior surface of the larynx. The posterior wall is even 

 broader above than below. The lateral parietes with the open- 

 ing for the tuba Eustachii (at the same elevation as the posterior 

 extremities of the inferior turbinate bones). 



The limit between the pharynx and O3sophagus is indicated 

 by: the narrowness of the tube, the paleness and the altered 

 direction of the muscular fibres of the latter. 



Muscles (see Myology). Fasciae: 1. F. pharyngea posterior arises from the 

 inferior surface of pars basilaris, tuba Eustachii, and serves for the attachment 



