310 HEALTH AND DISEASE 



0)-ujin. — From the sphenoid and palatine l)ones. 



Insertion. — Into the inner surlace of the lower jaw opposite the 

 masseter. 



Action. — To bring the lower jaw into contact with the upper, and to 

 move it from side to side in the process of mastication or grinding the food. 



Pterygoideus Externus. — A short, thick, fleshy muscle situated 

 within and in front of the articulation of the lower jaw with the temporal 

 bone. 



Origin. — From the sphenoid bone at the base of the skull. 



InM'.rtion. — Into the inner part of the neck of the lower jaw below the 

 articular condyle. 



Action. — To move the lower jaw forward and to one side in the act ol' 

 mastication. 



Temporalis. — This muscle lies on the side and front of the cranium, 

 extending into the temporal fossa. 



Origin. — From the outer surface of the parietal, scj[uamous temporal, 

 and frontal bones, in the temporal fossa, and from the sphenoid bone. 



Insertion. — Into the coronoid process of the lower jaw and the anterior 

 border of the same bone continuous with it. 



Action. — To assist in masticating the food by bringing the lower jaw 

 into contact with the upper and moving it from side to side. 



Stylo-Maxillaris. — This is a short, thick muscle situated in the region 

 of the throat. 



Origin. — From the styloid process of the occipital bone above in 

 company with another small muscle- — the digastricus. 



Insertion. — Into the angle of the lower jaw. 



Action. — By pulling the last-named bone away from the upper jaw it 

 opens the mouth. 



MUSCLES OF THE EXTERNAL EAR 



The external ear consists of a short bony tube projecting from the 

 petrous temporal bone, termed the external auditory canal, together 

 with three pieces of cartilage, and a number of muscles, vessels, and 

 nerves, &c. 



The Cartilages are distinguished as the conchal, the annular, and the 

 scutiform. The conchal cartilage forms the framework of all that portion 

 of the ear which stands erect. It presents a large vertical opening on one 

 side for the reception of sound, and is attached below to the annular 

 cartilage, a small ring of gristle connected with the auditory jDrocess of the 

 petrous temporal bone. The scutiform cartilage is a small, flat, somewhat 



