Edinger, The Cortical Optical Centres in Birds. 207 



In the thalamus it occupies the most dorso-lateral region of the 

 basal cerebral bundle and ends behind the chiasm after passing 

 laterad in the deepest layers of the mesencephalon in broad di- 

 varications. At least Marchi preparations do not enable us to 

 trace it further. Bumm has recognized the origin in the cortex 

 but not the terminus in the mesencephalon. It is Bumm's 

 " dorsale hirnschenkel abtheilung. " Birds also possess another 

 tract to the mesencephalon, the " Bundle der sagittalen Scheide- 

 wand " [so-named by Bumm but called by C. H. Turner 

 " tractus Bummi "] the course of which was also traced in de- 

 generation preparations. It does not end in the optic centres 

 but in a special nidulus lying cephalad of these and whose rela- 

 tion to the optic system is yet to be proven.^ 



Dr. Edinger then demonstrated this long associational tract 

 which appears first in birds. 



Since the present state of our knowledge warrants the view 

 that the cortex is the seat of those psychical functions which 

 are carried on consciously by means of reflection with employ- 

 ment of memory images, such a discovery of cortical tracts 

 connecting with niduli of special sensory apparatus has a high 

 degree of interest from the standpoint of comparative psychol- 

 ogy. It now becomes more easily intelligible that birds exhibit 

 in some of their activities very highly developed optical mem- 

 ory capacity. The lower terrestrial vertebrates may find all 

 their vital necessities accommodated for by the impression af- 

 forded by the sense of smell, but in the case of birds this would 

 not be advantageous. On the contrary, as they float far above 

 their food or roosts they must be able to recognize them by 

 means of vision and especially to distinguish them from moving 

 objects spuriously resembling their prey. Illustrations were 

 cited by the speaker and by the ornithologist, Dr. Wurn. 



[See editorial note elsewhere in this number.] 



^It may be recalled that Turner traced this tract from " frontal or the 

 fronto-median lobe " beneath the precommissure to the outer layer of the tectum. 

 His methods were such as permitted ambiguity. 



