214 Journal of Comparative Neurology. 



ganglion. The relations at this point receive further notice in 

 the paragraphs upon the trigeminal fibers to the m. levator 

 bulbi. 



As the sixth nerve passes out of the ganglion it is usually 

 in close relation with the r. ophthalmicus profundus. Beyond 

 this point there is considerable variation in the behavior of the 

 nerve. In one case it sends off two twigs each of which anas- 

 tomoses with a small twig arising independently from the Gas- 

 serian ganglion. The two resulting nerves innervate the m. 

 levator bulbi. One division of the main nerve then supplies 

 the m. retractor bulbi while the other division innervates the m. 

 rectus externus. In another case the twigs to the levator mus- 

 cle are absent and the part of the nerve which is destined for 

 the m. rectus externus divides. One division passes on either 

 side of the m. retractor bulbi. In still other cases the entire 

 nerve to the external rectus passes laterally of the retractor 

 muscle. 



./. — Trigeminal Tivigs to the M. Levator Bulbi. 



The case just mentioned, in which twigs from the fifth and 

 sixth nerve fuse to innervate the levator muscle, demands 

 special notice. It is evident here, either that the m. levator 

 bulbi is innervated from two central sources, or that there is an 

 interchange of fibers between the fifth and sixth nerves. My 

 observations upon this and other cases will admit of no other 

 alternative. 



In contrast, however, with the variation just cited, the 

 only fibers terminating in the levator muscle of two other heads 

 are derived wholly from the sixth nerve. In one of these a 

 small cluster of fibers passes from the r. ophthalmicus profun- 

 dus into the abducens as the two nerves leave the cranium and 

 while they are in close contact with one another. 



In the light of this conflicting evidence, it is not absolutely 

 certain that the entire innervation of the m. levator bulbi is by 

 the ophthalmicus profundus, as I have implied in a previous 

 communication (1901). It is certain, however, that all the 

 nerve supply to this muscle cannot come from the sixth nerve,. 



