OLFACTORY ORGAN 



269 



and Lemur:. In Ungulates, Elephants, and Edentates, further 

 complications have arisen, and the number of endoturbinals has 

 considerably increased secondarily (/.//. to nine in Orycteropus). In 

 Primates (Figs. 196 and 199), on the other hand, reduction has 

 occurred from the condition found in Lemurs. 1 



The ectoturbinals differ so greatly in the individual orders and 

 even species that they cannot be reduced to a common type. In 

 Marsupials, Insect! vores, Hyrax and Bats, they are few in number, 

 while in Ungulates, Elephants, Carnivores, Seals, Edentates, 

 Rodents, and in Echidna, they are more numerous : in Ornitho- 

 rhynchus the ectoturbinals are entirely wanting, as is also the case 

 in most Primates and to a less extent in Lemurs. 



According to the degree of development of the olfactory appa- 

 ratus, taking specially into account its cerebral portion (olfactory 



,* Eiidnt ii rhinitis 



Ectoturbinals --\\f 



~~* Endoturlindls 



Septum nasi 



FIG. 198. DIAGRAMMATIC TRANSVERSE SECTION THROUGH THE NASAL CAVITY 

 OF A MAMMAL, TO SHOW THE RELATIONS OF THE ENDO- AND ECTO- 

 TURBIXALS. (Modified from Paulli.) 



lobes, &c., cf. pp. 200, 228), we may distinguish between Mammals 

 which are macrosmatic (the majority of the mammalian orders), 

 microsmatic (c.y. Seals, Whalebone-Whales, Primates), and tnws- 

 matic (most Toothed Whales). 



Except in Monotremes, the nasal chamber communicates 

 with neighbouring cavities, such as the maxillary, frontal, and 

 sphenoidal sinuses (Figs. 196fi and 199): the two last-mentioned 

 cavities arise in connection with the nasal apparatus, and in forms 

 with a well-developed sense of smell may enclose olfactory folds ; 



1 Primates possess one to three ethmoturbinals, but traces of as many as five 

 have been recognised in the embryo. The nasotnrbinal in anthropoid Apes and 

 Man is also more or less reduced. 



In addition to a reduction or entire degeneration of these parts in Cetacea, 

 the nose is shortened and the nostrils have a dorsal position, some distance back 

 from the apex of the snout : in the toothed forms they unite and open by a 

 single valvular aperture. In this Order a series of paired "nasal sacs" are 

 present under the skin, the function of which is not known. 



