The Senses 



205 



In all animals the mucous membrane which lines the 

 nasal cavity is very delicate and filled with nervelets. 

 These nervelets unite and form a single nerve on each 

 side which passes to the brain and transmits the impres- 

 sions derived from the odours in the air. The thin bones 

 within the nostril, which, in dogs and deer, curl and re- 

 curl in delicate lines and 

 scrolls and thus expose 

 such a large surface to 

 the odour-bearing air, are 

 but poorly represented in 

 birds. The simple curve 

 of the bone in the nos- 

 trils of birds is very simi- 

 lar in structure to that 

 found in reptiles. 



The question whether 



vultures perceive their ^,,^^ 149.-Turln„al scrolls of dog. in a 



prey by sight or smell has '''"'^ *^^"^ ''""^' ^'^ *'^'" '""•'^ ''"'p'"'- 

 been decided in favour of the former sense. Lacking the 

 ability readily to distinguish delicate odours, we find 

 among birds none of the glands which are so common 

 among hair3'-coated creatures: the oil-gland is the only 

 one on the body, and this is practically odourless. But 

 slight as is the scent which diffuses from birds, it is 

 suflficient to enable a dog, with his wonderful keenness 

 of smell, to detect a crouching bird some distance 

 away. 



The woodcock of our inland swamps and marshes, 

 and the apteryx of New Zealand, probably have the 



