PACK. 



213 



pieces are found at its angles, formed either 

 from tlie ethmoid or from the orbitar plate of 

 the u|)]>cr maxillary bone. 



The inferior turtiinnted bones, (ossa s/mngiosa 

 v. turbinala iii/ima; Germ, die tnilern Muschel- 

 beinc) of an oval form, thin and spongy in their 

 appearance, are placed horizontally along the 

 lower partof the outer wall of the nasal cavities, 

 separating,' the middle from the inferior meatus, 

 and contributing to increase the surface of the 

 nose. Each hone presents two surfaces, two 

 borders, and two extremities. The internal 

 siir/'nce is rough, convex, and looks towards the 

 septum of the nose, which it sometimes touches 

 on one side when that partition inclines more 

 than usually to the right or left. The external 

 .w/r/i/ir is concave, exhibiting many small 

 fossae or pits; it looks towards the upper 

 maxilla and forms a part of the inferior meatus. 

 Both surfaces are very irregular or spongy and 

 are pitted by vessels, but especially by veins, 

 which ramify abundantly upon them. The 

 interior border is convex and thick, particu- 

 larly at its centre, where it descends towards 

 the floor of the nose. The vpper border is 

 thin and irregular, and presents from before 

 backwards, 1. a thin edge, which is attached 

 to the inferior turbinated crest on the nasal 

 process of the upper maxilla; 2. a process 

 (the lachrymal) which ascends towards the 

 curved process of the os unguis, with which and 

 with the adjacent part of the upper jaw-bone it 

 unites to complete the canal for the nasal duct ; 

 3. some irregular projections (etlimoidal pro- 

 cesses) which ascend and unite with the 

 ethmoid ; 4. a thin, curled, dog's-ear-looking 

 process (the auricular or maxillnry ), which, 

 descending and overhanging the internal sur- 

 face of the bone, is attached to the lower part 

 of the opening of the antrum, which it con- 

 tributes to circumscribe ; 5. an edge which is 

 articulated with the inferior turbinated crest 

 of the palate-bone. The orifice of the antrum 

 is situated just above the centre of this border, 

 and opens consequently into the middle mea- 

 tus. 



The extremities or angles are formed by the 

 union of the two borders ; the posttrior extre- 

 mity is more pointed than the anterior. 



Connexions. Each inferior turbinated is 

 united with four other bone, viz. the upper 

 maxillary, the lachrymal, the ethmoid, and the 

 palate. It is covered with the pituitary mem- 

 brane ; it contributes to enlarge the surface of 

 the nasal cavity, and to form a part of the 

 nasal canal and middle and lower meatus. 



Its structure is compact. 



Its development commences at the fifth month 

 by a single point of ossification. 



The vomer (Germ, das Pjlngscliurhein) is 

 of a quadrilateral figure, and resembles a 

 ploughshare; it is a single and symmetrical 

 bone, situated in the median plane, and forming 

 the posterior and inferior part of the septum 

 nasi. It has two lateral surface* and fiuir 

 bonli-rs. The surfaces, which are right and 

 left, are smooth, Hat, and lined by the pitui- 

 tary membrane; sometimes, when the bone 

 inclines much to either side of the nose, 



one of these surfaces in convex and the other 

 concave; they present an oblique groove or 

 grooves for the naso-palaline nerves and 



The nu/ierior border (or surface) is broad, 

 and may be termed the base of the bone ; it 

 presents a deep groove in the middle, which 

 receives the rostrum of the sphenoid, and on 

 each side of this are two plates or laminae 

 (sometimes called the aim) which are received 

 into fissures of the sphenoid on each side 

 of the rostrum, and which contribute to form a 

 longitudinal canal for theethmoida! vessels. 



The anterior border is oblique from above 

 downwards and forwards ; above it presents a 

 deep groove, which is a continuation of that 

 on the upper border, and which receives the 

 perpendicular plate of the ethmoid: below, 

 this border is nearly flat, where it is united to 

 the middle cartilage of the nose. 



The inferior border is the longest, and is 

 received into the grooved crest formed by the 

 united palatine plates of the superior maxillary 

 and palate bones ; in front this border extends 

 as far as the anterior nasal spine. 



The posterior border, thick above, thin be- 

 low, is oblique, slightly curved, and forms the 

 partition between the two posterior openings 

 of the nose. 



Connexions. The vomer is connected with 

 four bones, viz. the sphenoid and ethmoid 

 above, the superior maxillary and palate below : 

 it is covered with the pituitary membrane, and 

 forms, with the perpendicular plate of the 

 ethmoid and the middle cartilage, the septum 

 of the nose. 



Its structure is compact, and it is formed 

 of two thin lateral plates, which are distinct 

 above, but united interiorly. 



Its development occurs by a single ossific 

 point about the third month, and at birth it is 

 completely ossified. 



'I he os maxillare inferius (Germ, da* untere 

 Kiiinbackenbein, oder der Unterkiefer). This 

 single bone, which alone forms the lower jaw, 

 occupies the lower and lateral parts of the face ; 

 it is a flat, symmetrical bone, and bears some 

 resemblance in shape to a horse-shoe. It con- 

 sists of a middleor horizontal portion (the body), 

 and of two lateral ascending branches (the nwn), 

 which are connected with the body nearly at 

 right angles. 



The body is curved, nearly horizontal, in- 

 clining from before backwards, and a little 

 upwards, and presents two surfaces and two 

 borders. 



The anterior surface is convex, and has in 

 the centre a vertical line (criatu mentnlit ex- 

 teniu), which marks the union of the two 

 halves nf which the bone consists in the young 

 subject : this line terminates below in a tri- 

 angular eminence (the mental proem). The 

 vertical direction of the lower jaw at the sym- 

 phvsis, and its curved figure anteriorly, form- 

 ing what is termed the chin, are both charac- 

 teristic of the human race. From the angles 

 of the mental process arises mi each side the 

 external oblii/iie line, faintly marked in front, 

 but becoming distinct as it avend* diagonally 



