ORGANS OF SMELL. 397 



gold snuff-box, for a short time, and then the box be 

 cleansed with soap and water, still it will retain the odor 

 of musk for years. 



611. The sense of smell is conveyed to the brain by a 

 pair of nerves called the olfactory, which are spread on 

 the sides of the nostrils. 



613. Dr. Magendie says that the olfactory apparatus 

 ought to be described as a sort of seive, placed in the pas- 

 sage of the air, as it is introduced into the chest, and inten- 

 ded to stop every foreign body that may be mixed with the 

 air, particularly the odors. 



In all the terrestrial animals the cavity of the nostrils is 

 divided into two parts by a vertical partition, the whole 

 interior being lined by a soft membrane, called the schnei- 

 derian, or pituitary membrane. This is constantly kept 

 moist by glands which secrete a fluid for that purpose. 



This membrane is well supplied with blood-vessels, and 

 with nerves for the olfactory pair. These nerves in carni- 

 vorous animals are much larger than in those that live on 

 vegetables. 



614. In most animals the bony structure of this part of 

 the scull is exceedingly intricate, and therefore cannot be 

 described to the understandings of those who have no 

 previous knowledge of anatomy. We must consequently 

 refer those of our readers who wish to examine this 

 point more particularly, to some treatise on that subject. 

 The best way, however, is to take the head of some 

 quadruped, and with a fine saw divide the parts both 

 transversely and longitudinally. Such an examination, 

 assisted by a good description, will give the general stu- 

 dent all the information he may want on this subject in a" 

 few hours. 



615. Olfactory Nerves of the Duck. We give a single 

 longitudinal figure on this subject, in which the olfactory 

 nerves are peculiarly conspicuous, both from their size and 

 mode of distribution. This is the upper mandible ot a 



17* 



