874 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



The recti, or straight muscles, all take origin about the optic foramen and 

 radiate outward, being inserted in the globe of the eye on either side, 

 above and below, constituting thus the external and internal straight 

 muscles and the superior and inferior straight muscles. Of the oblique 

 muscles, the superior alone arises from the optic foramen and runs 

 forward over the superior and inner part of the orbit through a pulley 

 in the depression just within the inner extremity of the superior orbital 

 margin, then outward and backward beneath the superior straight muscle, 



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Fig. 397.— Scheme op the Action of the Ocular Muscles. (Landois.) 



and is inserted in the eyeball midway between the latter and the external 

 straight muscle, the cornea, and the optic nerve. The inferior oblique 

 muscle arises from the anterior portion of the edge of the orbit, and runs 

 by its tendon to be inserted beneath that of the external rectus muscle. 

 The function of the superior oblique muscle is to roll the eye downward 

 and inward, that of the inferior oblique muscle upward and inward, 

 although this may be accomplished by the different recti muscles acting 

 simultaneously. The above diagram indicates the action of the ocular 

 muscles (Fig. 397). 



