330 THE BIOLOGY OF BIRDS 



the semicircular canals are injured, the bird loses all power 

 of effective movement. When one is injured the result 

 is a particular disability, such as faUing backwards, which 

 varies according to the particular canal that is affected. 

 The semicircular canals are first seen in fishes, and are 

 present in all vertebrates with normally developed ears. 



According to Laudenbach (1905) there is a correspond- 

 ence between the degree of development of the semicircular 



Fig. 48. — Diagram of a bird's ear. c.A., anterior semicircular canal ; 

 C.P., posterior semicircular canal ; c.E., external semicircular canal ; 

 N., the cut end of the auditory nerve from the brain ; three branches of 

 the auditory nerve are shown dark ; u., the utriculus of the ear into 

 which the three semicircular canals open; d.e., the ductus endolym- 

 phaticus, rising from the sacculus, another chamber of the ear ; the 

 ductus endolymphaticus enters the brain-case and ends in the firm 

 membrane or dura mater surrounding the brain ; the sacculus also gives 

 off a slightly bent cochlea or lagena (l.), in which are seen the ramifica- 

 tions of one of the branches (s.b.) of the auditory nerve. 



canals and the precision of equilibration in flight. An 

 investigation of a representative series showed that the 

 semicircular canals were best developed in the swallow 

 and least developed in swimming birds. 



§ 3. The Other Sense- Organs 



Sense of Smell. — Only in a few birds has the sense of 

 smell been strictly demonstrated, e.g. in magpie, blackbird, 

 owl, and night-hawks ; and it may be said generally that 

 olfactory impressions are of relatively little importance 

 in birds, compared with mammals. What a contrast 

 between the wide, soft, moist nostrils of most mammals, 



