THE CORTICAL OPTICAL CENTRES IN BIRDS. ^ 

 By Dr. Ludwig Edinger. 



Synopsis of an Address at the Meeting of Southwest German Neurologists and 



Psychiatrists, i8gj. 



Dr. Edinger had demonstrated to the Association in former 

 meetings how gradually the cortex has developed in the animal 

 series from insignificant beginnings. The latest investigation 

 concerns the question, " Which fibre systems were earliest to de- 

 velop to or from this cortex ? " 



A year ago it was demonstrated to the Association that 

 the earliest cortical connections, appearing in reptiles, belong to 

 the olfactory apparatus (olfactory radiations and fornix). It is 

 now possible to locate a tract from the cortex to the optical 

 centres. This appears to be absent in reptiles but is so highly 

 developed in birds (pigeons) that it may be considered as the 

 strongest tract of the cerebrum. The tractus occipito-tectalis, 

 as it is termed by Edinger, arises near the brain base quite in 

 the occipital region and passes cephalad, curving ventrad ceph- 

 alad of the precommissure. It may be followed into the mes- 

 encephalon where the optic nerve terminates. The region of 

 origin of this bundle in birds is where the axial lobe is but im- 

 perfectly separable from the cortex and is accordingly not to be 

 distinguished from the former with certainty, but from its periph- 

 eral origin it is regarded as a cortical tract rather than the most 

 caudal portion of the radiations from the axial ganglion. The 

 tract becomes medullated some weeks after hatching exactly as 

 in the mammals where it has the same termini. 



The course was verified by serial sections and especially by 

 the results of degeneration. Three pigeons from which the 

 occipital region was removed by operation were preserved alive 

 for three weeks. In these the tract was completely degenerate. 



^Authorized translation from Arch. f. Psychiatric, XXVII, 3. 



