Olfactory Apparatus in Dog, Cat and Man 35 



have been used to represent this condition. In eases where the figures 

 used are original, they lack distinctness, which is, no doubt, due to the 

 uncertainty of knowledge of this region. 



The idea of a plexus of the nerve bundles is of earlier origin than 

 the work of Leveille, as will be shown by Figs. 10 and 13. These are 

 copies of the figures of Scarpa, 1785. The ideas of Leveille did not 

 differ esentially from those of Scarpa, and were, no doubt, strongly 

 influenced by them. Our knowledge at the present day concerning the 

 plexiform arrangement of the olfactory nerve bundles is practically that 

 of Scarpa. Much credit is due Scarpa for his excellent work, the facts 

 of which have formed a basis for the knowledge of that region to the 

 present time, as will be seen by the following resume of a part of the 

 second book of his Anatomicarum Annotationum. 



A series of nerve bundles varying in number with the subject come 

 from the apex of the bulb. These, covered by the meninges, pass through 

 the foramina of the cribriform plate and are spread out as nerves of 

 olfaction within the nose. The principal branches are arranged in an 

 internal and an external series. The internal send out filaments to the 

 nasal septum. When the nasal membrane is turned back from the 

 septum it is found to be filled with filaments of nerves running doAvn 

 in series. They difi^er in length, some often so long as to reach the 

 lowest base of the septimi and almost touch the floor of the nasal cavity. 

 Others descend only half way. Some pass perpendicularly, while others 

 are arched, as the posterior ones (Fig. 10). 



The external series is distributed far and wide through the upper 

 turbinal bones. The longest branches reach from the upper nares to 

 the lowest edge of the middle turbinated bones. These are perpendicular 

 at first and then recurved to the posterior. The posterior ones are 

 arched (Fig. 12). These nerves in their course from the cribriform 

 plate to the pituitary membrane form anastomosing plexiform connec- 

 tions. The plexiform nerve bundles are found in canals of the turbi- 

 nated bones of the nose, as is admirably shown in the figures of Scarpa 

 (Figs. 11, 12). Not many olfactory filaments go to the lower turbinals, 

 and he questions whether they are of much importance. 



There are no olfactory nerves to the membranes of the pituitary 

 sinuses, and hence these are not olfactory in function. 



His descriptions of the 5th nerve to the nose are practically those 

 of to-day. 



The following are Scarpa's own words concerning the olfactory 

 nerves : 



