130 EDWARD PHELPS ALLIS, JDN. 



to the profundus foramen, and extending backward toward 

 the dorsal edge of the trigemino-facial foramen. The surface 

 of origin of the muscle lies immediately dorsal to, and in 

 contact with, the surface of insertion of the ventro-anterior 

 head of the rectus externus, and immediately anterior to the 

 surface of insertion of the dorso-posterior head of the same 

 muscle. The dorsal and smaller head of the internus 

 separates from the ventral head shortly posterior to the point 

 where the latter receives its innervating branches from the 

 oculomotorius. Tm-ning dorsally and backward it comes into 

 contact Avith the ventral edge and inner surface of the rectus 

 superior, and there, gradually diminishing in size, disappears 

 without ever reaching tlie cartilage of the skull. 



My specimen thus shows a condition of the rectus internus 

 different from any of those described either by Schwalbe 

 (57), Tiesing (62), or Corning (14), and it will be ngain 

 referred to in describing the eye muscles. The ventral 

 division of the oculomotorius passes outward between these 

 two divisions of the internus muscle, lying dorsal to the one 

 and ventral to the other. It lies wholly in front of, and hence 

 ventro-anterior to, the rectus superior. 



The oculomotorius is accompanied in its course between 

 these two heads of the internus muscle by the ramus 

 ophthalmicus profundus, but the latter nerve here runs in 

 the opposite direction to the oculomotorius, that is, forward 

 instead of backward from its foramen. Both nerves lie 

 anterior to the rectus superior, and, as they cross, are closely 

 pressed against each other, as Schwalbe has said, but with- 

 out any observable interchange of fibres. 



After the oculomotorius has passed the profundus, crossing 

 ventral to it, it continues downward and backward, reaches 

 the dorsal surface of the rectus inferior, and then soon 

 passes downward and forward around the hind edge of that 

 muscle. There it continues forward for a time, closely 

 applied to the ventral surface of the inferior muscle, and here 

 sends a large branch to that muscle. 



Where the oculomotorius turns downward and forward 



