1248 



A MANUAL OF ANATOMY 



the ventral ends of the second, or hyoid, and third, or thyro-hyoid, visceral 

 arches. The union between the buccal and pharyngeal parts is indicated by 

 the V-shaped sulcus terminaUs, between the two limbs of which is the foramen 

 ccccum, or upper end, of the thyro-glossal duct. This foramen represents the 

 persistent upper extremity of the embryonic median diverticulum, called the 

 ductus thyro-glossus, from the lower part of which the isthmus of the thyroid 

 body is developed. The tuberculum impar makes its appearance as a round 

 eminence in the median line, opposite and between the first visceral clefts. 

 Behind it, and separated from it by a groove, is the furcula, which is a forked 

 eminence, mesially placed opposite the second and third visceral arches, and 

 resembling a horseshoe. It gives origin to the epiglottis and aryteno-epiglot- 

 tidean folds. The ventral ends of the second and third visceral arches of 

 either side coalesce, and the united ends of these arches join each other in the 

 interval between the tuberculum impar and the furcula, forming the copula. 

 It is from the copula that the root of the tongue is formed. It is developed 

 from it as two elevations, which take an upward and forward direction, 



Tuberculum Impar 



Furcula — 



Fig. 509.— The Visceral Arches of the Embryo (Posterior View) (His). 



Mandibular Arch 

 Hyoid Arch 



V. Fifth Arch 



III. Thyro-hyoid Arch 



IV. Fourth Arch 



diverging at the same time in a V-shaped manner, so as to embrace the buccal 

 part. After the pharyngeal and buccal portions of the tongue have coalesced, 

 a V-shaped groove persists for some time, indicating the line of union of the 

 two parts of the organ; and in adult life this is represented by the sulcus 

 ferminalis. 



The Soft Palate. 



The soft palate, or velum penduhim palati, is a movable musculo- 

 aponeurotic curtain situated at the back part of the hard palate, 

 w'here it projects dov^'n Wards and backwards into the pharynx. 

 Anteriorly it is attached to the posterior border of the hard palate, 

 laterally it is connected with the side of the tongue and the Wall of 

 the pharynx, and postero-inferiorly it presents a free border. Its 

 surfaces. Which occupy an oblique plane, are antero-inferior or 

 buccal, which is concave, and postero-superior or pharyngeal. Which 

 is convex and looks towards the naso-pharynx. The postero- 

 inferior border at its centre presents a conical process, called the 

 uvula. On either side of the base of the uvula there are two 

 prominent folds of mucous membrane, which extend outwards 

 and downwards in a diverging manner. These folds constitute the 



