MUSEUM OF COMrARATIVE ZOOLOGY. 159 



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

 aspect by the nasoturbiiiaL In advance and beneath these plates, as 

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

 turbinal lies.* This l)one acts as a sieve to wai'm the current of air 

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

 particles which pass through the upper half of the maxilloturbiual pass 

 directly to tlic 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 

 maxilloturbiual 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 tlie 

 endoturbinal plates. Direct contact of the inspiratory currents through 

 the space between the maxilloturbiual 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 directed immediately inward, or inward and upw\ard. 

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

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

 ber above the level of the ti'ansverse lamina, and lie atrainst the 

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

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

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

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

 current 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, tlie invitation 

 fur 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 olfoctory level. The transverse lamina, there- 

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



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

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

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

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

 f^. noctula, but is probably true of all mammals. 



