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D. DAVIDSON BLACK 



postero-median muscular bands respectively). Its origin and 

 insertion are similar to the first mentioned muscle and are shown 

 in the next dissection. 



Lateral to these muscular bands and situated on a lower plane, 

 there is seen a broad sheet of muscular tissue whose fibers are 

 more or less parallel to the anterior convex border of the max- 

 illary element. The relations of this mass are more clearly 

 brought out in the next dissection. 



Fig. 10 Diagram of structures exposed in dissection of orbital fossa from above; 

 third stratum. I. P.M., inferior postero-median muscular band; Mx., maxillary- 

 element; Ps., point of attachment of proboscis; Pl.M., muscular mass probably- 

 belonging to the pterygoid group; R.I., rectus inferior muscle; S, deep fossa be- 

 hind maxillary element. Note: the arrangement of themuscle/.P.M. and the one 

 overlying it is such as to suggest the use of the term 'retractor bulbi.' Other let- 

 tering as in figure 8. 



Third stratum (fig. 10). The entire muscular mass represent- 

 ing the levator palpebrae superioris and the superior portion of 

 the postero-median muscular band were removed. The vessels 

 and nerves were also removed with these. It was noted that a 

 small branch of the ophthalmic artery entered the bulbus oculi 

 in the mid-line at the lower margin of the fibrous optic nerve. 

 With the exception of the rectus lateralis the muscular mass in 

 relation to the eye received its innervation in a very irregular 

 fashion from branches of the third nerve. The sixth nerve, as 



