30 Life and Health 



which curve about within the nasal cavities so as to increase 

 the surface of the air .passages of the nose. 



The vomer serves as a thin and delicate partition between 

 the two cavities of the nose. It is so named from its resem- 

 blance to a ploughshare. 



The largest bone in the face is the inferior maxillary, 

 or lower jaw. It has a horseshoe shape and supports the 

 lower set of teeth. 



41. Sutures of the Skull. The edges of the bones of the 

 outer shell of the skull are joined together in a peculiar and 

 admirable manner. In adult life these edges, which are not 

 unlike the teeth of a saw in appearance, fit into each other 

 and grow together, suggesting the dovetailed joints used by 

 the cabinet-maker. When united these serrated edges look 

 almost as if sewed together ; hence their name, sutures. This 

 manner of union gives elasticity and strength to the skull. 



In infants the corners of the parietal bones do not yet 

 meet, and the pulsations of the brain may be seen and felt 

 under these "soft spots," or fontanelles ("little fountains") as 

 they are called. Hence a slight blow to an infant's head may 

 cause serious injury to the brain. As old age creeps on, the 

 cap of the skull becomes a solid dome of bone, with alj trace 

 of the sutures lost. 



42. The Hyoid Bone. Under the lower jaw is a little 

 horseshoe-shaped bone, called the hyoid bone, because it is 

 shaped like the Greek letter upsilon (Y). It really belongs 

 to the skull, although it lies in the neck. The root of the 

 tongue is fastened to the bend of the hyoid, and the larynx 

 is hung from it as from a hook. This bone serves to keep 

 open the top of the larynx, and to it are attached the muscles 

 which move the tongue. 



Experiment 12. To locate the hyoid bone. Allow the neck to 

 rest in its natural position. Gently grasp with the thumb and fore- 

 finger the front of the throat, just above the " Adam's Apple." The 

 hyoid bone can be plainly felt 6n a level with the lower jaw and about 

 one inch and a half behind it. 



