ON THE OLFACTORY SENSE OF BIRDS 



Walter Neuhaus 



Zoological Institute of the University Erlangen-Niirnberg, 

 Germany 



INTRODUCTION 



" Rerum naturae scriptores non parum inter se dissentiunt circa avium 

 olfactum. Sunt enini qui sensum hunc segneni admodum et obtusuni in 

 alotibus esse doceant, dum alii contra acri et exquisite Volucres olfacto 

 praeditas esse contendunt. ..." In spite of numerous investigations the 

 inconsistencies in our knowledge on the olfactory sense of birds has not 

 changed since Scarpa in 1789 so accurately described the knowledge of his 

 time on this subject. I hope I will be able to show that these inconsisten- 

 cies are due to peculiarities in the olfactory complexes in the birds. Mr. E. 

 Fink has performed the first experiment under my guidance, and has 

 assisted me with the others. 



THE MORPHOLOGY OF THE OLFACTORY ORGAN 

 OF THE BIRD 



The nasal cavity of the bird is surrounded by the premaxillary, maxillary, 

 nasal and palatine bones, and is also divided into two parts by the septum. 

 The air passes through the outer openings and the primary and secondary 

 Choana. The nostrils are small or even closed in the Steganopodes and 

 Sphenisci. Each half of the nose is divided by three muscles : the lower 

 (Praeconcha), the middle (Concha), and the upper (Postconcha) (Fig. 1). 

 In many birds the last one is only a small bulge, or is entirely missing. 

 There are olfactory sense cells in most birds, but only in the region of the 

 Postconcha (Fig. 2). Depending upon the size of this region the number 

 of olfactory cells varies very much indeed. The exact numbers are not 

 known, in contrast to the mammals, and especially the dog. The structure 

 of the avian olfactory region as basically similar to the mammalian one, 

 with its olfactory cells, supporting cells, basal cells and the glands of 

 Bowman. 



The olfactory cell nerve fibres ascend to the Pars bulbaris in the Lobus 

 olfactorius, where they end. The secondary olfactory pathways are less 

 well developed in the birds than in the mammals (Fig. 3). A pathway to 



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