310 HEALTH AND DISEASE 



Origin. From the sphenoid and palatine bones. 



Insertion, Into the inner surface 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 Extemus. 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. 



Insertion. 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 of 

 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, squamous 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 process of the 

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



