842 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Examination of the structure of the membrane lining the nasal cavities 

 shows marked points of distinction between the region to which the 

 olfactory fibres have been traced and other portions of the nasal cham- 

 bers. The area of distribution of the olfactory nerve is termed the 

 regio olfactoria, and in the main embraces the upper part of the septum 

 and the upper part of the middle turbinated bone. The remainder of 

 the nasal cavity is called the regio respiratoria. The olfactory region 

 has a thicker mucous membrane than the respiratory part. It is covered 

 by a single layer of cylindrical epithelial cells, which contain yellow 

 pigment in sufficiently large quantity to serve even by the naked eye to 

 distinguish this part of the nose from the respiratory passages. The 

 latter division of the nasal cavity is covered by ciliated epithelium and 

 contains tubular glands and serous, acinous glands. In the olfactory 

 region are found between the ordinary BB 



cylindrical epithelium cells peculiar 



Fig. 363.— Diagram of the Structure 

 of the Olfactory Region, after 

 Exnek. (Briicfce.) 



C C, the terminal net-work of the olfactory nerve in 

 which both the so-called olfactory cells (A) and cylin- 

 drical cells are imbedded. 



Fig. 364.— Diagram illustrating the 

 Mode of Connection of the Ol- 

 factory and Cylindrical Cells 

 with the Terminal Net-work of 

 the Olfactory Nerve. (Brucke.) 

 B B, cylindrical epithelial cells ; A, olfactory cell ; 

 D, protoplasmic mesh-work in which the olfactory nerve 

 terminates. 



spindle-shaped cells with a large nucleus, containing nucleoli, and sending 

 up between the cylindrical cells a narrow projection which in various 

 animals terminates in delicate projecting filaments. These peculiar 

 olfactory cells are said to form a direct communication with the fibres 

 of the olfactory nerve. 



It is probable, according to Exner, that these cells do not 

 directly unite with the olfactory fibres, but through the mediation of a 

 net-work of protoplasmic prolongations of these cells lying below their 

 bases. Examination has further shown that not only these long so-called 



