MUSCLES OF THE EYE. 517 



containing the molar and the last or largest prsemolar tooth. This 

 will expose the lateral aspect of the eyeball and a muscle (ptery- 

 goid) extending obliquely from the mandible to the floor of the 

 orbit. There is also brought clearly into view the superior max- 

 illary artery and the superior maxillary division of the 5th nerve. 

 Both extend along the floor of the orbit laterad of the eyeball to the 

 infraorbital foramen (Fig. 50, Fm. inf. or.), from which point they 

 are called infraorbital artery and nerve. They should be carefully 

 removed. Two of the muscles of the eyeball will appear, 3VE. rectus 

 ventralis, M. rectus later alls. Raise the eyeball somewhat with 

 a scalpel handle and cut the pterygoid muscle at its origin in the 

 floor of the orbit. Note that the edges of the recti muscles slightly 

 overlap near their origin, but separate like the sepals of a flower as 

 they extend cephalad toward the eyeball. Separate them, and 

 trace first the M. rectus lateralis to its attachment on the eyeball, 

 .removing the loose fibrous substance with scissors. Do not injure 

 the tendon of the ventral oblique (see 1406). 



Pass a scalpel handle entad of the free edge of the muscle, raise 

 it and free it from the underlying tissue with a tracer. When free, 

 raise the muscle by the scalpel handle and make it tense. It will 

 be seen to terminate in a broad ribbon-like tendon which is inserted 

 into the sclerotic at the caudal margin of the white zone of the eye- 

 ball (Fig. 126, Z. a.). . 



1406. M. obliquus ventralis (inferior), the ventral or inferior 

 oblique muscle. In clearing away the fibrous tissue from the ball 

 to expose the lateral rectus, this muscle also will be exposed. It 

 appears as a circular band overlapping the ventral rectus. Sepa- 

 rate the body of the muscle from the other tissues, and lift it up 

 with the scalpel handle as for the lateral rectus, and it will be seen 

 to insert itself by a broad tendon along the edge and cephalad of 

 the tendon of the lateral rectus. The tendons of these two muscles 

 form a right angle. Raise the eyeball with a scalpel handle and 

 trace the ventral oblique to its origin from the orbital surface of the 

 maxilla just laterad of the Os lachrymale (just laterad of the "h" 

 of the abbreviation " O. Ich." in Fig. 56). 



1407. M. rectus ventralis (inferior), (Fig. 126, M. r. vntr.). 

 This appears on the ventral side of the eyeball. Draw it out so as 

 to show the attachment ; then dissect the body of this muscle as 

 directed for the lateral rectus, and raise it in order to note its inser- 



