Dissection of Sheep's Head. 243 



orbital membrane on the outer margin of the orbit ; united 

 at the origin of the principal muscles of the eye, they proceed 

 about three-quarters of an inch further together, ascending 

 along the direction of the most external muscle of the eye, 

 mz.y the external rectus, and then they part company ; one 

 small twig passing straight up to the Lachrymal gland, the 

 other continuing on in its first direction, to be distributed to the 

 muscles and integument on the superior and posterior margin 

 of the orbit. Of the Nasal branch we shall treat later on. 



The tendinous insertion of the superior rectus into the 

 sclerotic coat beneath the lachrymal gland should be next 

 noted. The inner surface of this muscle is in apposition, 

 near its insertion, with the suspensorius muscle (found in all 

 Quadrupeds up to the Quadrumana), and with the tendon of the 

 superior oblique ; and, near its origin, with two stout nerves, 

 m%., the Third, by which it is itself supplied, and the Nasal 

 branch of the Fifth. A twig from the fifth will also be found 

 supplying this muscle. 



The External Rectus muscle may be next cleaned. This 

 muscle has a similar origin and insertion to the Superior 

 E-ectus, hut is supplied by a separate nerve, the Sixth nerve, 

 a very fine thread, which reaches the muscle near its origin, 

 and on the edge nearest to the Superior Rectus. 



Factors of the Pedicle of the Eyeball. We have 

 now, at this stage of the dissection, disclosed the following 

 factors of the stalk, or pedicle, of the eyeball : ^nearest 

 to the middle line is the tmj Fourth nerve ; next to it the 

 origins of the levator palpebrae superioris, and superior 

 rectus muscles ; then the Third nerve, the Nasal branch of the 

 Ophthalmic division of the Fifth nerve, the twig from the Fifth 

 supplying the superior rectus, and the Sixth nerve, all occupy- 

 ing the narrow slit between the origin of the rectus superior, 

 and that of the rectus externus, which comes next ; and lastly, 



