180 
recti, and are inserted into the superior posterior surfaces 
of the eyes. These posterior slips are the rotatory slips of 
the superior oblique muscles, and their function* is to 
cause a rotation of the eye on its optical axis, a movement 
which is very exceptional among fishes as among higher 
vertebrata, and which is doubtless a special adaptation to 
the peculiar mode of life of the Pleuronectide. The 
extent of the rotation may be as much as one-eighth of a 
circle. 
Inferior oblique muscles (0)/. inf.).—Both right and 
left muscles originate in the left prefrontal in the same 
region as that from which the superior muscles take 
origin. The left muscle passes upwards and backwards 
along the external wall of the orbit and is inserted into 
the inferior middle surface of the eye-ball. The right 
muscle takes origin a little in front of the left, and, as in 
the case of the superior muscles, the proximal portions 
cross each other. It then passes through the ethmoidal 
fenestra with the superior muscle of its side, and passes 
upwards and backwards along the external wall of the 
right orbit, and is inserted in a corresponding position to 
that of the left eye. The inferior are slightly thicker than 
the superior muscles. 
The superior recti (7. swp.).—These are strong muscle 
bundles originating in a strong oblique partition crossing 
the eye muscle canal. They run forwards in the latter, 
slowly diverging from each other, and emerge on either 
side of the interorbital septum. They are inserted into 
the superior and posterior margins of the eye-balls under- 
neath the rotatory slips of the superior oblique muscles. 
The inferior recti (7. inf.).—Also rather thick muscles 
which take origin far back in the eye-muscle canal at 
about the transverse level of the articulation of the head 
* Bishop Harman—Journ. Anat. Phys., vol. xxxv., pp. 1-40, 1899. 
