4 8o HISTORY OF THE HUMAN BODY 



single turbinal found in certain groups of reptiles, where its 

 function is wholly olfactory. The bone which forms the 

 framework of this part is usually distinct from the ethmoid, 

 and forms the " inferior turbinated bone " of human anatomy. 

 The name " maxillo-turbinal " is to be preferred, as it better 

 expresses its relationship. 



The remaining turbinalia, all of which are olfactory, form 

 a set of parallel projecting ridges, arising from the lateral wall 

 of the cavity and arranged in series from above downwards; 

 the most dorsal of these is borne, at least in part, by the nasal 

 bone and is termed the naso-turbinal; the others are ethnio- 

 turbinalia, that is, they arise from the ethmoid. The total 

 number of turbinalia, not counting the maxillo-turbinal, is 

 most usually five, but larger numbers are met with up to eleven, 

 the number found in certain edentates. Besides these primary 

 turbinalia which, although arising from the outer wall, yet 

 nearly reach the inner one, there is often present a variable 

 number of secondary and even tertiary turbinalia filling the 

 spaces left free by the first. These relations are shown in 

 Fig. 130, A and B, which represent diagrammatic cross sec- 

 tions of nasal .cavities ; A, with primary turbinalia alone, and 

 B, with secondary and tertiary ones. The primary ones are 

 termed end o turbinalia from their position, to which all the 

 rest are contrasted as ecto turbinalia. The various possibili- 

 ties which arise from rolling the edges of the laminae are also 

 shown; the edge may be rolled inwards (B, I), or outwards 

 (B, IV), or again there may be two free edges either rolled 

 in different ways (B, III), or in the same way (B, II' and 

 II"). This latter possibility, when viewed from the free inner 

 surface, appears like two separate turbinalia, but is morpho- 

 logically a single one. 



Such involved forms of turbinalia are the rule rather than 

 the exception among quadrupedal mammals, the greatest de- 

 gree of complexity being reached by the ungulates (Fig. 130, 

 C), rodents and carnivores, a structure which gives them a 

 high degree of power in the sense of smell. These structures 

 become much reduced in the anthropoids; and in Man (Fig. 



