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Median optic fasiculiis (Plate XIV, Fig. 7). — 'I'liis is a 

 well-defined bundle which arises from the corpus posterius 

 and passes to the cephalad portion of the optic lobe. There 

 it turns laterad and fuses with the external optic tract. 

 Throughout its entire course this tract lies ectad to the 

 mesencephalic ventricle. In passing from its nidulus to the 

 external optic tract this fasciculus describes an ectally convex 

 curve. 



In 1889 Dr. Perlia(') destroyed the retina of one eye of a 

 young chick and then allowed the specimen to live for 

 several months. The brain was then removed and prepared 

 for microscopical examination. As a result of the extirpa- 

 tion it was found that, in the optic lobe connected with the 

 injured eye, several tracts had atrophied. One of these 

 atrophied tracts was the one just described. This experiment 

 seems to demonstrate that this tract is connected with the 

 optic nerve. Dr. Perlia has christened this tract the " median 

 optic fasciculus." 



Third nerve (Plate XIV, Fig. 12). — In the avian brain 

 the root of the oculo- motor nerve is quite prominent. 

 Arising from its nidulus in the caudo-dorsad portion of the 

 diencephalon and passes ventro-laterad to its external root. 



Mesencephalic root of the third nerve (Plate XIV, Fig. 3). 

 — In addition to the main root of the third nerve, there is 

 another tract which appears to be connected with that nerve. 

 This tract arises in the optic lobe,entad to the mesencephalic 

 ventricle. Describing a curve the convexity of which is 

 directed dorsad, this tract passes mesad to the peduncular 

 nidulus. The majority of these fibres pass through this 

 nidulus and decussate at the meson. There are fibres which 

 connect the two niduli, but I have not been able to trace any 

 of these fibres into the third nerve root;(-) 



1 " Ueber ein neues Opticus Centrum beim Huhne." Von Dr. Pkri.ia, Augenarzt 

 in Frankfurt a. M. Aus dem Senkenberg'schen Institute (Prof. Weigert). Albrecht von 

 Graefe's Archiv f. Ophthalmologic, Btl. XXXV, s. 20-24, taf. ii. 



2 A tract homologous with the one just described is found in reptiles. See "Notes 



