MUSEUM OF COMrARATIVE ZOOLOGY. 159 



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

 aspect by the nasotui'binal. 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 cniTcnt of air 

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

 particles wliich pass through the upper half of the raaxilloturbinal pass 

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

 distance from their lateral attachments to the primary terminal convolu- 

 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 wliich 

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

 laterally through this opening or drawn upwai'd between the lobes of the 

 endoturbinal plates. Direct contact of the inspiratory currents through 

 the space between the maxilloturbinal and the septum must be incon- 

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

 these parts. A small passage between the nasoturbinal and the sep- 

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

 above indicated are dii'ected immediately inward, or inward and upward. 

 In these directions no continuity with the aii'-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 cuiTcnts may be as- 

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

 olfactory surftices. This condition of rest doubtless goes on wdiile ordi- 

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

 cm-rent to be passing in and out along the lower portion of the nasal 

 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 tlie 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 olfixctory level. The transverse lamina, there- 

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



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

 crest into the snout, wlicre it ends in the prominent swelling at the upper lateral hor- 

 der. Near its end it is concave outward, the concavity receiving a little crest-like fold 

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

 r. noctula, but is probably true of all mammals. 



