ANATOMY OF THE OLFACTORY ORGAN 



33 



Grassi and Castronovo (1889) in the dog, and subsequently 

 was identified by Alcock (1910) in the pig. In this mammal 

 the epithelium of the intermediate zone is thicker than that 

 of the respiratory region and thinner than that of the 

 olfactory region. Besides basal cells it possesses two 

 types of epithelial cells, ciliated cells like 

 those of the respiratory epithelium and 

 non-ciliated sustentacular cells like those 

 of the olfactory region. It also contains 

 many olfactory cells, but these cells are 

 not as numerous in the intermediate zone 

 as they are in the olfactory region 

 where they are said to make up about 

 seventy per cent of the cells present. It 

 is plain from the accounts given that 

 the intermediate zone is a region of 

 transition between the two chief nasal 



FIO.O 



preparation of an 



regions, the olfactory and the respiratory. 



In most verte- 



a pike (Esox) 

 which not only the 

 cell body and the 

 basal nerve - fiber 

 process are well 

 shown, but also the 

 long peripheral ol- 

 factory flagellum. 

 After Jagodowski, 

 1901, Fig. 8c. 



5. Polymorphic Cells. 

 brates the olfactory cells exhibit great 

 uniformity of structure. In the fishes, 

 however, Dogiel (1887) has called attention 

 to a polymorphism among these elements, 

 and he has described in addition to the ordinary type of 

 spindle-shaped olfactory cell, cylindrical olfactory 

 cells and conical olfactory cells. These three types 

 have been identified by Morrill (1898) and by Asai 

 (1913) in a selachian (Mustelus) and by Jagodowski 

 (1901) in the pike (Esox). To what extent this 

 polymorphism occurs in other vertebrates and how 

 important it is for a right understanding of the action 

 of the olfactory organ has not yet been determined. 



