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 thinness, 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 terminating at length in a kind of apex, which passes under the superior turbinated 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 correct 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 inferior turbinated bone in the dog is very small, but it is curiously complicated. 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. The 'lachrymal duct' is the channel through which the superfluous tears are conveyed to the lower parts of the nostril. A long canal here commences, and runs down and along the maxillary bone. It is very small, and terminates in the cuticle, in order that the highly sensitive membrane of the nose may not be excoriated by the tears occasionally rendered acrimonious in inflammation of the eye. The oval termination of this duct is easily brought into view by lifting the nostril.