240 THE HUMAN SPECIES 



Fig. 119). This region of mucous membrane, unlike the regio 

 respiratoria, has no ciliated epithelium, but columnar cells, 

 longitudinally striated, alternating with spiral cells which reach 

 to the surface of the mucous membrane as hair-like processes, 

 and whose inner ends communicate with the end-branches of 

 the olfactory nerves by means of fine varicose filaments. In 

 birds, reptiles and amphibia the olfactory cells on the mucous 

 surface bear 4-10 stout cilia, some rigid, some in wave-like 

 motion. Mammals are similar to the other three orders (birds, 

 reptiles and amphibia) in having olfactory cells connected with 

 nerves. In the Vertebrates below the mammals, however, the 

 olfactory ciliae begin to assume the histological characters of the 

 olfactory organs of the Invertebrates. 



Man and the mammals are like the other Vertebrates in that 

 odours are perceived not only by inspiring air from the front 

 of the nostrils but also from behind, when the flavour of food as 

 it is swallowed can be appreciated ; according to Nagel this is 

 a very important arrangement by which the secretion of the 

 digestive juices in man and animals is stimulated. 



Very interesting facts have been observed upon the acuteness 

 of the sense of smell in man. 1 The following traces of various 

 scents could be detected : 



Oil of rosemary . ^ milligramme per litre of air 



Oil of peppermint . -L 



Artificial musk . ii 



Chlorphenol . . 0^00000004 



Jager's researches show that some people have the power of 

 differentiating relatively insignificant odours of individuals as 

 well as family odours, and even the peculiar scent attaching to 

 the inhabitants of the same village (spezifische dorfgeriiche !). 



Speaking generally, man, not only in a state of civilisation 

 but also the primitive savage (e.g., Papuan), has a much less 

 acute sense of smell than that possessed by animals. Civilised 

 man has probably lost a good deal of the " nose " that he once 

 possessed. 



The delicate and keen sense of smell in animals is astonish- 

 ing, especially in wild horses, wild cattle and wild boar ; 



1 Munk-Schultz, p. 556. 



