Anatomy. — *'0n tiro Xerves of Yertehrnte.'i ai)re>'ing bi Structure 

 until tht Nerves of hivertehrates.'" By Dr. A. B. Drooglkkvkk 

 FoRTUYN. (Communicated by Prof. J. Boekk). 



(Communicated in the meeting of November 30, 1918). 



As a well-known fact the olfactory cells in the mucous membrane 

 of the nose of Vertebrates are "Sinnesnervenzellen" or "conducting 

 sense-cells" as 1 propose to call them, nnless thej have received 

 already another English name. (The word "sensory nerve-cell" may 

 then be reserved to "sensibele Ganglienzelle"). They are sense-cells 

 whicii are not surrounded by nerve-fibres, but whose cell-body directly 

 passes into a process with all the characteristics of a nerve-fibre. 

 These nerve-fibres, the fila olfactoria, constitute the nervns olfactorius. 

 So the olfactoiT nerve deviates in its structure from all the other 

 nerves of the vertebrated animals. The truth of this remark may 

 already be deduced from the fact that in Vei-tebrates besides in the 

 olfactory mucous membrane conductive sense-cells are only found 

 in the retina (I'od- and cone-cells) and perhaps in the pineal organ. 

 So all the nerves of the Vertebrates with exception of the olfactory 

 nerve are devoid of nervous processes of conducting sense-cells. On 

 the contrary the majority of the nerves of in vertebrated animals do 

 contain processes of conductive sense-cells, which in these animals 

 are always spread about the whole body in all kinds of sense-organs. 

 Often in Invertebrates nerves are composed exclusively of fascicles 

 of neurites of conducting sense-cells as is the case in the olfactory 

 nerve of the Vertebrates. From this I conclude that we have to look 

 upon the olfactory nerve of the Vertebrates as a nerve constructed 

 in a way which is often met with i)i Invertebrates, and nowhere 

 else in vertebrated animals. 



Another striking difference between the nerves of vertebrated and 

 invertebrated animals is this that in the Invertebrates ganglion-cells 

 are generally disperse<l along tfie whole course of the nerve either 

 separately or in groups, ganglia. In the nerves of Vertebrates, 

 however, they ai-e totally wanting or they are accumulated in very 

 few ganglia (spinal ganglia or those of the nerves of the brain). Now 

 if one reads (e.g. in the review on ihis subject by Prof, van Wuhk 

 in these Proceedings, Vol. XXVI, 1918) that also in the nervns 



