EVE 
233 
The muscles of the eyeball and of the third eyelid are 8 in 
number, of which 6 serve to moye the eyeball. 
Four recti, viz. 
superior, inferior, internus, and externus arise from the orbit in the 
vicinity of the optic nerve ; the first three are innervated by the 
Lert EYE or THE ComMMON FOWL FROM FRONT AND BEHIND. 
0.if. Musculus obliquus inferior; R.if. R.int. R.s. R.e. M. rectus inferior, internus, superior, 
and externus ; Q. M. quadratus; P. M. pyramidalis. 
n. oculomotorius or 3rd cranial nerve, and the externus by the n. 
abducens, or 6th cranial nerve. 
The m. obliquus superior arises from the ethmoidal margin of 
the orbit, passes between the olfactory and the first branch of the 
trigeminal nerve, is supplied by the n. trochlearis or 4th cranial 
nerve, and is inserted upon the upper and inner side of the 
eyeball. 
The m. obliquus inferior arises below the optic nerve, and is 
inserted laterally from the inferior 
rectus ; it is supplied by the 3rd 
cranial nerve. 
The nictitating membrane is 
moved by two muscles, both of 
which are innervated by the 6th 
cranial nerve. The m. quadratus 
is a trapezoid muscle, arising with 
a broad base from the hinder sur- 
face of the eyeball, and forming 
with its narrow margin, which is 
directed towards the optic nerve, 
a pulley for the long tendon of 
the m. pyramidalis. The latter 
arises from the nasal or median 
surface of the eyeball, passes into 
a tendon, which runs above the 
optic nerve through the pulley and 
goes over on the anterior side of 
the eye into the nictitating mem- 
brane. 
VENTRAL VIEW OF THE NERVES OF THE 
Lert EYEBALL oF Rhea americana. 
V.r.7. First branch of nervus trigeminus ; 
VI, Nervus abducens, innervating the mus- 
culus rectus externus, m. pyramidalis, and 
m. quadratus; R.s. R.inf. Rint. Obl. inf. 
Branches of the nervus oculomotorius (see 
Brain); ciliares, Ciliary nerves supplying the 
internal muscles of the eye, e.g. Crampton’s 
muscle ;—the swelling at the root of these 
nerves is the ciliary ganglion. 
The latter is a transparent, slightly whitish membrane, 
which arises with a broad base from the upper outer margin of the 
eye as a duplication of the conjunctiva. 
Contraction of the pyra- 
