MUSCLES OF THE EAR AND NECK. 71 



Internal Pterygoid, from the pterygoid fossa of the sphenoid bone, and the 

 tuberosity of the palate, into the angle and inner surface of the ramus of 

 the jaw, as high as the dental foramen. Action, raises and draws for- 

 ward the lower jaw; a triturating muscle of mastication. Nerve, inferior 

 maxillary. 



External Pterygoid, by 2 heads, the upper, from the pterygoid ridge on the 

 greater wing of the sphenoid, the lower from the external pterygoid plate, 

 and the tuberosities of the palate and superior maxillary bones, into a 

 depression in front of the condyle of the inferior maxillary, and the inter- 

 articular fibre-cartilage. Action, to draw the jaw forwards; a triturating 

 muscle of mastication. Nerve, inferior maxillary. 



Between the two heads of the external pterygoid muscle passes the internal 

 maxillary artery. 



MUSCLES OF THE EAR. 



Tensor Tympani, from the under surface of the petrous portion of the tem- 

 poral bone, the cartilaginous Eustachian tube, and its own osseous canal, 

 into the handle of the malleus. Action, to draw the membrana tympani 

 tense. Nerve, branch from otic ganglion. 



Laxator Tympani Major, from the spinous process of the sphenoid and the 

 cartilaginous Eustachian tube, through the Glasserian fissure to the neck 

 of the malleus just above the processus gracilis. Action, to relax the mem- 

 brana tympani. Nerve, tympanic branch of the facial. 



Laxator Tympani Minor, from the back of the external meatus, passes be- 

 tween the layers of the membrana tympani into the handle of the malleus 

 and processus brevis. Action, to relax the membrana tympani. Considered 

 a ligament by many anatomists (the lig. mallei posticum). 



Stapedius, from the interior of the pyramid, through the orifice at its apex 

 into the neck of the stapes. Action, to depress the base of the stapes. 

 Nerve, filament from the facial. 



MUSCLES OF THE NECK. 



Platysma Myoides, from the clavicle, the acromion, and the fascia covering 

 the pectoral, deltoid, and trapezius muscles, into the lower jaw, the angle 

 of the mouth, and the cellular tissue of the face. Action, to wrinkle the 

 skin, and depress the mouth. Nerves, facial and superficial cervical. 



Sterno-cleido-mastoid, 11 by two heads from the sternum 12 and the clav 

 icle 13 at its inner third, into the mastoid process of the temporal bone, 

 and the superior curved line of the occipital. Action, to depress and 

 rotate the head. Nerves, spinal accessory, and branches of the cervical 

 plexus. 



