SMELL IN ANIMALS. 391 



the pharynx, but the anterior nares, instead of being placed near the extremi- 

 ties of the upper jaw, are found far back on the top of the head, where they 

 form sometimes, as in the sperm whale and narwhal, one, but usually two, 

 blow holes, through which the water taken in by the mouth in feeding, and 

 stored up in two strong muscular cavities, can be forcibly expelled. The high 

 position of these openings readily brings them to the surface when the animal 

 desires to breathe, an act which can be accomplished even whilst the mouth 

 is submerged and engaged in catching prey. The nasal fossae of the Cetacea, 

 exposed as they are to the frequent passage of water through them, as well 

 as of air, have little or no concern in the function of smell. Thus, in the 

 true whales, the olfactory nerves are proportionally very small, and judging 

 from what takes place in ourselves when water or even solutions of odorous 

 substances are poured into the nose, it may be conjectured that they do not 

 distinguish the presence of odorous particles in the water, but only that of 

 those conveyed to them through the air taken in during inspiration. In the 

 porpoises and dolphins, however, the olfactory nerves are absolutely wanting ; 

 and these creatures, therefore, can possess no true sense of smell, though they, 

 and indeed the other Cetacea, may receive impressions of an irritating char- 

 acter from substances diffused through the water, acting on the extremities 

 of the branches of the fifth pair, which, 'as usual, supply the nasal mucous 

 membrane. 



Amongst Birds generally, the sense of smell does not appear to be so highly 

 developed, as to qualitative power in the individual, though it may be as 

 acute as in Mammalia. There is no longer a cribriform plate to the ethmoid 

 bone, for the olfactory nerves pass each through a single foramen. The nasal 

 cavities are proportionally smaller and less complex in their interior than in 

 the Mammalia, but the turbinated bones are sometimes convoluted, and even 

 laminated. The posterior nares often coalesce before they open into the pha- 

 rynx. The anterior nares are never provided with movable cartilages, as in 

 the Mammalia. These openings differ much in size, position, and structure ; 

 they are generally wide and open, but are narrow in the heron, often pro- 

 tected by stiff feathers, as in the crows, or covered by a scale, as in the rasorial 

 birds ; they are usually placed on the sides of the bill, but sometimes at its 

 base ; and occasionally, as in the apteryx, at its apex. Judging from the rel- 

 ative size of the chief turbinated bone, and of the olfactory nerves, the wading 

 birds appear to possess the most perfect sense of smell. In the vultures, also, 

 the nose is much prolonged, and the olfactory nerve is large ; they are said to 

 smell carrion at very great distances. Nevertheless, the idea still sometimes 

 entertained, that the vulture scents its dead prey from the enormous altitudes 

 at which it flies, has been disproved, the discovery of its food being effected 

 through the agency of vision. 



In Reptiles the sense of smell seerns to be less developed than in birds ; there 

 are few or no complications of the surfaces of the nasal fossae. The posterior 

 nares open, in the Saurians, into the pharynx ; but in the Chelonia and 

 Ophidia through the palate, into the mouth. In the crocodiles the nostrils 

 can be closed when he animal is beneath the water ; and these apertures 

 being placed at the end of their long snout, they are able to lie almost com- 

 pletely submerged, concealed, and watching for their prey. 



The perfect Amphibia also present two posterior nares, opening through 

 the palate into the mouth ; but in the Proteus family this opening is placed 

 so far forwards that it passes through the upper lip ; in the Proteus itself, 

 the nasal mucous membrane is plicated, as in Fishes. In their early fish-like 

 larval condition, the organs of smell in the Amphibia are merely simple 

 depressions or recesses, like these parts in fishes, but they are provided with 

 cilia. 



The sense of smell is probably, as already stated, somewhat modified in 

 aquatic animals ; but it is, nevertheless, judging from the size of the olfactory 

 nerves and lobes, actively exercised in Fishes. These animals do not inhale 

 the atmosphere into their bodies, for they have no lungs. The nasal fossae 

 form two blind recesses or culs-de-sac, opening externally on the fore part of 

 the head, but in almost all cases shut off posteriorly from the mouth or pha- 

 rynx. The water, through which medium the odorous particles must be 



