128 ANATOMY OF THE DOMESTIC FOWL 



Origin. By two heads infero-laterally to the optic foramen. 



Insertion. To the postero-external side of the eyeball. 



Shape. Short, fan-shaped. 



Relations. Internally, with the eyeball; externally, with the bony 

 wall of the orbit. 



Action. Pulls the eyeball outward. 



Rectus Interims (Fig. 26, No. B, 2). (Synonym. Rectus 

 medialis.) 



Location. Inner side of the eyeball. 



Origin. From the supero-anterior border of the optic foramen. 



Insertion. To the sclera on the anterior portion of the eyeball. 



Shape. Thin, fan-shaped. 



Relations. Internally, with the eyeball and with the pyramidalis; 

 externally, with the bony wall of the orbit. 



Action. Pulls the eyeball inward. 



THE MUSCLES OF THE EAR 



Circumconcha Tensor tympani 



Circumconcha (Fig. 7, No. 32). Location. Surrounds the exter- 

 nal ear. 



Origin and Insertion. The Circumconcha, surrounding the periph- 

 ery of the ear, is adherent to the skull and loosely to the skin, and 

 is attached to the outer terminus of the supra-occipital crest. 



Relations. Internally, with the skull; externally, with the skin. 



Action. Relaxes the tympanum. 



Tensor Tympani (Fig. 7, No. 31). Location. External to the 

 quadrate and to the external auditory meatus. 



Origin and Insertion. From the surface of the quadrate and the 

 inner end of the quadra to- jugal to the inner surface of the tympanum. 



Shape. A few fibers. 



Relations. Internally, with the quadrate and the quadra to- jugal; 

 externally, the integumental duplicature. 



Action. Tenses the tympanum. 



FUNCTIONS OF MUSCLES 



To cause the feathers on the top of the head to lie flat: 



Dermo-frontalis. 



To raise the feathers along the superior part of the neck and along the dorsal 

 region: 



Dermo-dorsalis. 



