68 



APPLIED ANATOMY. 



In the Annals of Surgery (vol. xix, 1894, p. 653) is recorded a case of the 

 author's in which a man, while drunk, fell and struck his chin on the curbstone. A 

 fracture was produced through the symphysis above and branching to each side of 

 the genial tubercle below. This small median piece was drawn back into the throat 

 nearly to the hyoid bone, and suffocative symptoms were marked. These disap- 



Geniohyoid muscle Geniohyoglossus muscle 

 FIG. 78. Anteroposterior section of the tongue and floor of the mouth, near the midline. 



peared when the detached piece was drawn forward and wired in place. The piece 

 was drawn backward by the geniohyoid and geniohyoglossus muscles. The digas- 

 trics may also have aided in depressing the fragment (Figs. 77 and 78). 



The most usual site of fracture is in the neighborhood of the mental foramen. 

 This is located just below the second premolar tooth (sometimes between the first 

 and second). This foramen and the large socket for the canine tooth farther 



Temporal muscle 



Masseter muscle 



Buccinator muscle 



Mylohyoid muscle 

 Digastric muscle 



FIG. 79. Fracture of the lower jaw in the region of the mental foramen, showing the line of fracture and the influ- 

 ence of the muscles in producing displacement. 



forward weaken the bone somewhat in this region. The jaw is strengthened behind 

 the mental foramen by the commencement of the anterior portion of the ramus and 

 by an increase in the size of the mylohyoid ridge on the inner surface. The jaw is 

 also protected by the thick masseter muscle and fracture is most liable to occur just 

 in front of it. This constitutes the typical fracture of the lower jaw (Fig. 79). 



