94 SMELL, TASTE, ALLIED SENSES 



area is believed to correspond to the vomero-nasal organ 

 of the higher vertebrates and the lateral area to the true 

 olfactory receptor of these forms. 



In some amphibians the distinction between a lateral 

 and a median organ is much more evident than in fishes 

 (Fig. 21). The lateral organ is the one that conducts the 



Flo. 20. Diagram of the median face of the left nasal cavity of man; the small circle marks 

 the position of the vomero-nasal organ in the nasal septum. 



newly established air current from the external naris to 

 the choana and hence corresponds to the olfactory organ 

 proper. The median cavity is less involved in this cur- 

 rent and is believed to represent the vomero-nasal organ. 

 In certain sauropsida such as the alligators and tur- 

 tles the vomero-nasal organ has been said to be at best 

 only poorly developed, though so far as turtles are con- 

 cerned this opinion is not shared by one of the most 

 recent workers, McCotter (1917). In birds the organ 

 is claimed to be entirely absent, but in lizards and in 

 snakes it is highly differentiated (Fig. 22). Here the 

 olfactory apparatus consists of a well-developed organ 



