40 POULTRY DISEASES 



and thicker walled than in mammals. The ampulla are the 

 upper and back canals with bony walls. The cochlea is a 

 tul)e thinly covered at the blind end and contains the cuticular 

 cochlea. At its point it is broadened for the formation of the 

 lagena. The cavity of the cochlea is divided by the spiral 

 walls, the scala vestibuli and the scala tympani. These walls 

 are visible in the vestibulum so that they may be 

 seen at the beginning of the cochlea. 



Organs of Smell 



The olfactory nerve, after merging from the 

 cranium through the olfactory foramen passes 

 down and spreads out, terminating in filaments 

 on the mucous membrane of the nasal passage. 



Organs of Taste 



Fig. 11. CocH- 



^Tnth^f^I' ^^^® tongue is considered the taste organ. In 



Hen most birds the thick stratified squamous epithel- 



2 I'emidJcuiar ^^^ dorsal surfacc is little adapted for taste per- 

 canais; 3, am- ccptiou. The ninth ucrvc is the nerve of taste. 

 CO Jhfea; 5,' The lingiial branch of the trigeminus is missing. 

 fenestra ^vesu- Filamcuts of the first and second branches of the 

 tiestra 'cochlea- trifacial, wliicli is broadened in the mucous mem- 

 "^' brane of the hard palate, furnish taste filaments 



to that part. Taste buds are then found on both 

 the tongue and hard palate. 



Organs of Touch 



The organs of touch are the skin and feathers. The skin 

 consists of an epidermis and dermis. The skin contains no 

 sweat glands. In fowls and many other birds there is pro- 

 vided a tail (rump) gland. This is a tubular gland which 

 secretes an oily substance that is carried to the surface 

 through a common duct. The bird, by obtaining some of this 

 oil substance on its beak, oils the feathers. This oil preserves 

 the feathers from becoming dry and brittle and prevents loss 

 from w^eather conditions. In a few birds special touch and 

 taste perception is provided by the edges and point of the 

 beak. The dermis (corium) is well developed and furnishes 

 ample muscular means for the raising and lowering of the 

 feathers. The corium is thin. Papillary bodies are present 

 only in a few areas, as the region of the eyes and on the toes. 

 Thickened epithelial elevations are noted on the ventral por- 

 tion of the toes, where there is great wear as a result of contact 

 with the ground. 



