216 THE OLFACTORY ORGAN, BY PROFESSOR BABUCHIN. 



chiefly occasioned by the granules ; and the isolation of the 

 several nerve fibrils then becomes almost an impossibility, as 

 we find to be the case in the spherules of the regio olfactoria. 

 I am very much inclined to believe that the same relations are 

 repeated in the retina, and perhaps in other parts of the 

 nervous system. 



The tractus olfactorius consists exclusively of medullated 

 nerve fibres, which have no sheath of Schwann. After they 

 have reached one of the two projections, which in the Torpedo 

 are placed at the sides of the great hemispheres, they pene- 

 trate into the reticular substance, gradually lose their medullary 

 layer, and unite there with numerous small nerve cells, of 

 which some again are bipolar, whilst others are multipolar. 

 This is the essential fact I have discovered from my re- 

 searches upon the Plagiostomata. I am unable to pursue the 

 examination of the other constituents of this apparatus. All 

 the relations just described respecting the origin of the ner- 

 vus olfactorius are present also in the higher Vertebrata, 

 however different their structure may at first sight appear to 

 be. The fibres of the olfactory tract arise directly from a 

 finely granular reticular mass, whether in the form of sphe- 

 rules or otherwise. 



This mass is everywhere surrounded by small nerve cells. 

 The processes which run inwards into the olfactorius and 

 the cerebrum everywhere undergo conversion into medullated 

 nerve fibres, which here and there unite again with fresh nerve 

 cells. A difference consequently only exists in a topographical 

 point of view, which must obviously be regarded as of merely 

 secondary importance, and belongs to another chapter of this 

 work. 



[During the final revision of these sheets Exner has published in 

 the Wiener Sitzungsberichte the results of his researches upon the 

 olfactory mucous membrane of the Frog. According to what I can 

 learn from his short provisional communication, the branches of the 

 olfactory nerves break up into a plexus* between the connective tissue 

 of the mucous membrane and the epithelial layer, and from this the 

 central processes both of the so-called olfactory cells and of the epi- 

 thelial cells arise. The trigeminal fibres form a wide-meshed plexus 

 in the connective tissue of the mucous membrane. STRICKER.! 



