Muscles of The Eye.

Muscles of The Eye.

These consist of four straight muscles, two oblique, and one retractor. The straight muscles pass from the depth of the orbit forward on the inner, outer, upper, and lower sides of the eyeball, and are fixed to the anterior portion of the fibrous (sclerotic) coat, so that in contracting singly they respectively turn the eye inward, outward, upward, and downward. When all act together they draw the eyeball deeply into its socket. The retractor muscle also consists of four muscular slips, repeating the straight muscles on a smaller scale, but as they are only attached on the back part of the eyeball they are less adapted to roll the eye than to draw it down into its socket. The two oblique muscles rotate the eye on its own axis, the upper one turning its outer surface upward and inward, and the lower one turning it downward and inward.