MUSEUM OF COMPARATIVE ZOOLOGY. 150 



an endoturbiual, the space between them being defined on the median 

 aspect by the nasoturbinal. In advance and beneath these plates, as 

 well as being more or less embraced by the endoturbinals, the maxillo- 

 turbinal lies.* This bone acts as a sieve to warm the current of air 

 entering the olfactory region, and to exclude extraneous particles. The 

 particles which pass through the upper half of the maxilloturbinal pass 

 directly to the ectoturbinals and the plates of the endoturbinals for the 

 distance from their lateral attachments to the primary terminal couvolu- 

 tions or endings. The current passing through the lower half of the 

 maxilloturbinal is received within the space below the level of the eth- 

 moturbinal, and is chiefly respiratory. A large opening exists between 

 the nasal chamber and the superior maxillary sinus, partly within which 

 the ectoturbinal plates lie. The lower current may be deflected in part 

 laterally through this opening or drawn upward between the lobes of the 

 endoturbiual plates. Direct contact of the inspiratory currents through 

 the space between the maxilloturbinal and the septum must be inc< >n- 

 siderable, by reason of the close relation, if not contact, existing between 

 these parts. A small passage bet\s r een the nasoturbinal and the Bep- 

 tum would permit some to pass. It will be seen that all the currents 

 above indicated are directed immediately inward, or inward and upward. 

 In these directions no continuity with the air-passage exists. The cur- 

 rents in time must impinge upon the sides and roof of the nasal cham- 

 ber above the level of the transverse lamina, and lie against the 

 cribriform plate. Within this restricted area the currents may be as- 

 sumed to cease, and their odor-bearing particles to fall gently upon the 

 olfactory surfaces. This condition of rest doubtless goes on while ordi- 

 nary respiration continues. So it is conceivable for a gentle respiratory 

 current to be passing in and out along the lower portion of the nas.il 

 chamber, while the air is at rest unloading itself of its odoriferous parti- 

 cles above the transverse lamina. When the air is sniffed, the invitation 

 for its ascent into the olfactory chambers is marked, — an act probably 

 accompanied by partial elevation of the soft palate, by which means the 

 respiratory current through the nose is suspended, and the air com- 

 pelled to ascend to the olfactory level. The transverse lamina, there- 

 fore, has great functional significance. The parts contained above this 



* The maxilloturbinal is continuous forward through the moans of a well-defined 

 crest into the snout, where it ends in the promineni swelling at tin- upper lateral l>or- 

 der. Near its end it. is concave outward, tin' concavity receiving a little crest-life 



on the outer side of the snout. The above description applies to tin- parts as seen in 



/". noctula, lull is prohal.lv true of all mammals. 



