530 ANATOMICAL TSCBNOLOGY. 



their attachment. The oblique muscles are so differently attaclied from those in man that 

 the action could hardly be the same (Quain, A, I, 377). It would seem from the anatomi- 

 cal arrangement that the ventral oblique would simply rotate the eyeball laterad and the 

 trochlearis would rotate it mesad. 



§ 1415. The nervous supply is given in the Table of cranial nerves (§ 1392), distri- 

 bution of the 3d, 4th, 6th and 7th nerves. The nerves may be made out on a fresh or alco- 

 holic specimen by following the genera] directions for dissecting nerves in §§ 1008, 1037. 



GLOBUS OCULI— EYEBALL. 



§ 1416. How to Obtain the Eyeball. — The one exposed in dis- 

 secting the muscles may "be severed from the head by cutting the 

 muscles near their middle and the optic nerve about 1 cm. from the 

 ball ; or a fresh eye may be exposed as described for studying the 

 muscles (§ 1405) and then severed as just described. In case it is 

 undesirable to injure the skull, or the eye of an ox or sheep is to 

 be obtained, grasp the lids successively, and turning the concavity 

 of the curved scissors toward the eyeball, sever the connection with 

 the lids. Grasp the membrana nictitans and draw the eyeball 

 cephalad. Keeping the concavity of the scissors toward the ball, 

 cut its fibrous and muscular connections with the orbit ; cut also 

 the optic nerve about 1 cm. from the ball. 



After the eyeball is removed, carefully free it from all tissue 

 except the membrana nictitans and the lateral and dorsal recti 

 muscles. These should be left to enable one to determine the 

 aspect of the eye. 



§ 1417. Nobe the following :— (A) In form, the eyeball of the cat 

 is spheroidal and somewhat pointed cephalad (Fig. 126). (B) The 

 cephalic third {cornea, § 1421) is transparent and continuous with (C) 

 the sclerotica (§ 1421), which forms the rest of the ectal wall of the 

 eyeball. (D) N. opticus, at the caudal part of the eyeball enters 

 the large cylindrical optic nerve. 



§ 1418. Iris at Pupilla (Fig. 126). — Upon looking into the cor- 

 nea there will be seen a golden-yellow circular curtain, the iris. 

 This curtain is not complete, but in the middle is an opening, the 

 pupil. The form of the pupil in the cat is circular when fully 

 dilated, as in a cat killed with chloroform. When partly contracted 

 it is elliptical, but when fully contracted it is a dorso-ventral slit. 

 These various forms are readily seen in a living cat's eye by trans- 

 ferring the cat from a dim into a brilliant light. 



§ 1419. Images Formed by the Eye. — If the eye is perfectly 

 fresh, so that the cornea is transparent, rub some strong glycerin on 



