THE ETHMOID BONES. 169 



CHAPTER X. 



ANATOMY OF THE NOSE AND MOUTH; AND DISEASES OF THE NOSE 



AND OTHER PARTS OF THE FACE. THE SENSE OF SMELL; THE 



TONGUE ; THE LIPS ; THE TEETH ; THE LARYNX ; BRONCHOCELE ; 

 PHLEGMONOUS TUMOUR. 



The Ethmoid Bones. THERE is some difficulty in describing the ethmoid 

 bones ; but we shall not, however, deviate far from the truth if we give 

 the following account : 



A great number of small hollow pedicles, proceed from and form around 

 the cribriform plate ; as they move downwards, they project into distinct 

 vesicles or cavities, smaller and more numerous behind, fewer in number 

 and larger in front ; and each of them not a simple cavity, but more or 

 less convoluted, while the long walls of those cells are of gossamer thin- 

 ness, and as porous as gauze. They even communicate, and are lined, and 

 externally wrapped together, by the same membrane ; the whole assuming 

 a pear-like form, attached by its base or greater extremity, and decreasing 

 in size as it proceeds downwards ; the cells becoming fewer, and termi- 

 nating at length in a kind of apex, which passes under the superior turbi- 

 nated bone, and forms a valve between the nasal cavity and the maxillary 

 sinuses. If to this is added, that the olfactory or first pair of nerves abut 

 on these cribriform plates, and pass through their minute openings, and 

 spread themselves over every one of these cells, we have a tolerably cor- 

 rect picture of this portion of the ethmoid bones. This nerve has different 

 degrees of development in different animals, in proportion to their acuteness 

 of smell. There is comparatively but little necessity for acuteness in the 

 horse. The ox has occasion for somewhat more, especially in the early 

 part of the spring, when the plants are young, and have not acquired their 

 peculiar scent. In the sheep it is larger, and fills the superior portion of 

 the nasal cavity ; but in the dog it seems to occupy that cavity almost to 

 the exclusion of the turbinated bones. It is also much more fragile in 

 the dog than in the ox, and the plates have a considerably thinner 

 structure. 



The ethmoid bone of the horse or the ox may be removed from its 

 situation with little injury ; but that of the dog can scarcely be meddled 

 with without fracture. Below it are the two turbinated bones ; but they 

 are reduced to insignificance by the bulk of the ethmoid bone. The in- 

 ferior turbinated bone in the dog is very small, but it is curiously com- 

 plicated. 



The meatus contains three distinct channels ; and the air, loitering, as it 

 were, in it, and being longer in contact with the sensitive membrane by 

 which it is lined, contributes to the acuter sense of smell. The larger 

 cavity is along the floor of the nasal duct. It is the proper air-passage ; 

 and because it has this important function to discharge, it is out of the way 

 of violence or injury. 



