232 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



the eve. It branches before reaching the ophthalmic branch of 

 the 5th ; the branches passing on either side of this nerve. 



IV and VI. Pathetic and Abducent. I consider these two 

 nerves together because there is a great variance of opinion as 

 to their presence or absence in the various Amphibia. 



Osborn in his discussions of the Amphibian brain claims to 

 have found both of these nerves in the Necturus, though he fails 

 to show the Vlth in any of his drawings and to make any definite 

 statement about either. In his drawings he gives the Vlth nerve 

 as arising from the roof of the 4th ventricle, at a point which cor- 

 responds to the cerebellum. 



Fish failed to demonstrate the IVth in Desmognathus. 

 Kingsley failed to find it in the larva Amphiuma, but Mrs. Gage 

 found it in a very rudimentary condition in the adult Diemycty- 

 lus. 



As to the Vlth nerve Kingsley says it is not found in the 

 larva Amphiuma; Osborn, as stated at the beginning of this 

 topic, omits it from his figures ; while Reissner and Ecker de- 

 scribe it in the Frog, and Fisher finds it in Siredon and Nec- 

 turus. With these facts in view I retraced my work, studying 

 carefully my serial sections and the many brains which had 

 been dissected as well as those isolated by 20 per cent, nitric 

 acid, and I have come to the conclusion that the IVth nerve 

 is not present in Necturus, and if the Vlth is, it has no sepa- 

 rate origin. My reasons for this statement are the following : 



1. In serial sections I was unable to find anything that cor- 

 responded to the IVth nerve at the place where Osborn gives 

 its origin, i. e., in front of the cerebellum. Xor could I find 

 anything which would correspond to the origin of the Vlth. 



2. Finding that by studying the brain alone I was unable 

 to find the origin of these nerves in question, I decided to dis- 

 sect out the muscles of the eye and see if from this I could 

 trace the nerves. After a careful dissection in which as far 

 as I could see the nerves remained intact I arrived at the fol- 

 lowing results: The muscles of the eye are supplied by the 



Illrd and by branches of the Ophthalmic division of the Vth. 

 All six muscles of the eye were supplied by these nerves as well 



