64 ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



its posterior extremity is attached to the similarly named crest of the palate bone. Between 

 the superior and middle turbinated bones is situated the superior meatus of the nose, which is 

 short and developed only in the posterior portion of the nasal fossa?. Between the middle and 

 inferior turbinated bones (the latter structure being an independent bone) is the middle meatus, 

 in which, covered by the middle turbinated bone, there is a bulging of the ethmoidal wall, the 

 ethmoidal bulla, a rudimentary turbinated bone, and another rudimentary turbinal (the os naso- 

 turbinale of the mammalia) is the sickle-shaped uncinate process (Figs. 81 and 102), which is also 

 covered by the middle turbinated bone. It articulates with a process of the inferior turbinated 

 bone (see below) and helps to close the orifice of the maxillary sinus. Between the uncinate 

 process and the ethmoidal bulla is a wide fissure, the infundibulum, which leads both into the 

 orifice of the frontal sinus and into the ethmoidal cells; its orifice in the nasal fossa is known as 

 the hiatus semilunaris (Fig. 101). 



The ethmoidal cells communicate partly with one another, partly with the air-cells of the 

 adjacent bones, and in all cases, either directly or indirectly, with the nasal fossae. 



The ethmoid bone is completely preformed in cartilage. Ossification commences late (in the fifth month of em- 

 bryonic life) and proceeds from the lamina papyracea and the middle turbinated bone. In the new-born, the two laby- 

 rinths have already ossified as far as the superior turbinated bone, but they are not connected, since the cribriform and 

 perpendicular plates do not possess ossific centers until the first year of life, when they gradually effect a bony union of 

 the two labyrinths. The remainder of the perpendicular plate does not ossify until the fifth year. 



THE INFERIOR TURBINATED BONE. 



While the two upper turbinated bodies are portions of the ethmoid bone, the inferior one 

 (concha nasalis inferior) (Figs. 79, 81, 82, and 98) is an independent structure and it is also the 

 largest of the three. It is a thin roughened bony plate, the free margin of which is turned upon 

 itself and slightly rolled up. It consists of a body and of three processes. 



The narrow, leaf-shaped body is placed in the sagittal plane. It is convex toward the nasal 

 septum, concave toward the lateral nasal wall, broader in front than behind, and is provided with 

 many depressions and small foramina. The anterior portion of the lateral border articulates 

 with the conchal crest of the maxilla (Figs. 81, 101, and 102), and the posterior portion of this 

 border is attached to the similarly named crest of the palate bone. 



The largest of the three processes is the maxillary process (Fig. 82), which is directed down- 

 ward and outward, and closes a considerable portion of the orifice of the maxillary sinus (see Fig. 

 101). The lachrymal process (Figs. 61 and 82), passing forward and upward, articulates with 

 the lower border of the lachrymal bone by the lachrymoconchal suture, and forms a portion of 

 the wall of the nasal duct (nasolachrymal canal) (Fig. 79). The ethmoidal process (Figs. 81, 82, 

 and 102) is directed upward and backward and articulates with the uncinate process of the 

 ethmoid bone in the region of the orifice of the maxillary sinus. 



The inferior turbinated bone ossifies in immediate connection with the ethmoid bone in the fifth month of em- 

 bryonic life. 



1 



THE LACHRYMAL BONE. 



The lachrymal bone (Fig. 78) is an approximately rectangular bony plate, very thin and 



frequently even perforated, situated in the inner wall of the orbit between the frontal process of 



