On a Non-striped Muscle of the Orbit. 325 



section of the nerve, was produced by the active contraction 

 of the retractor and recti, and that its reprojection by sub- 

 sequent irritation was a reposition. Schiff regarded the pro- 

 jection of the bulb as due to the action of the obliqui : the 

 movements of the lids he considered to be passive, and due 

 to those of the bulb. 



Kemak, on the other hand, believed that the narrowing of 

 the palpebral fissure was due to a relaxation of the levator 

 palpebral superioris, accompanied by a spasmodic contraction 

 of the orbicularis. Moreover, he conceived that the sym- 

 pathetic acted upon the voluntary muscles of the lids about 

 the eye. 



Miiller considers that it is now no longer necessary to dis- 

 cuss the various probabilities respecting the influence of the 

 sympathetic upon the voluntary muscles of the eye, as a 

 complete series of unstriped muscles have now been ob- 

 served, which will serve as a foundation for explaining the 

 movements in question. 



These muscles consist of three divisions : — 



1st, In the orbital cavity of mammals, a membrane (mem- 

 brana orbitalis), consisting of unstriped muscles with elastic 

 tendons, exists, which, by irritation of the cervical sympa- 

 thetic, projects the contents of the orbit, especially the bulb, 

 forwards. Retraction is produced by the transversely-striped 

 retractor. In man, the orbital muscle is much reduced in 

 size, and the retractor is wanting, so that a distinct projec- 

 tion of the bulb does not follow irritation of the sympathetic, 

 as Wagner and H. Miiller himself have observed. 



2d, The projection of the nictitating membrane in mam- 

 mals is mostly due to the retractor bulbi under the influence 

 of the N. abducens. Its withdrawal depends on some un- 

 striped muscles which are under the influence of the sym- 

 pathetic. In hares, however, the withdrawal is due to a 

 transversely striped muscle, which is not supplied by. the 

 sympathetic but by the oculo-motorius. In man, the lid 

 and its muscles are rudimentary. 



3d, The upper and lower lid possess in man, and in very 

 many mammals, unstriped muscles, which have the power 

 of drawing them back. They are more feeble in the upper 



