ANIMALS, 



m 



it will be found that the acuteness of smell bears a proportion in all animals 

 to the extent of surface which this membrane displays ; and hence, in the 

 dog and cattle tribes, as well as in several others, it possesses a variety 

 of folds or convolutions, and in birds is continued to the utmost points of 

 the nostrils, which in different kinds open in very different parts of the 

 mandible* 



The frontal sinuses, which are lined with this delicate membrane, are 

 larger in the elephant than in any other quadruped, and in this animal the 

 sense is also continued through the flexible organ of its proboscis. In 

 the pig the smelling organ is likewise very extensive : and in most of the 

 mammals possessing proper horns it ascends as high as the processes of 

 the frontal bone from which the horns issue. 



It is not known that the cetaceous tribes possess any organ of smell ; 

 their blowing-holes are generally regarded as such ; but the point has been 

 by no means fully established. We are in the same uncertainty in respect 

 to am.phibials and worms ; the sense is suspected to exist in all the former, 

 and in several of the latter, especially in the cuttle-fish, but no distinct 

 organ has hitherto been traced out satisfactorily. 



In fishes there is no doubt ; the olfactory nerves are very obviously 

 distributed on an olfactory membrane, and in several instances the snouts 

 are double, and consequently the nostrils quadruple, a pair for each snout. 

 This powerful inlet of pleasure to fishes often proves fatal to them from 

 its very perfection ; for several kinds are so strongly allured by the odour 

 of marjorum, assafcetida, and other aromas, that by smearing the hand over 

 with these substances, and immersing it in the water, they will often flock 

 towards the fingers, and in their intoxication of delight may easily be laid 

 hold of. And hence the angler frequently overspreads his baits with the 

 same substances, and thus arms himself with a double decoy. 



There can be no doubt of the existence of the same sense in insects, 

 for they possess a very obvious power of distinguishing the odorous pro- 

 perties of bodies, even at a considerable distance beyond the range of 

 their vision : but the organ in which this sense resides has not been satis- 

 factorily pointed out ; Reimar supposes it to exist in their stigmata, and 

 Knoch in their anterior pair of feelers. 



The general organ of hearing is the ear, but not always so ; for iii 

 most of those who hear by the Eustachian tube only, it is the mouth, and 

 in the whale tribes the nostrils or blow-hole. It is so, however, in all the 

 more perfect animals, which usually for this purpose possess two distinct 

 entrances into the organ, a larger and external, surrounded by a lobe ; and 

 a smaller and internal, opening into the mouth. It is this last which is 

 denominated the Eustachian tube. The shape of the lobe is seldom found 

 even in mammals similar to that in man, excepting among the monkey 

 and the porcupine tribes. In many kinds there is neither external lobe 

 nor external passage. Thus, in the frog, and most amphibious animals, 

 the only entrance is the internal, or that from the mouth ; and in the ceta- 

 ceous tribes the only effective entrance is probably of the same kind ; for, 

 though these may be said to possess an external aperture, it is almost im- 

 perceptibly minute. It is a curious fact, that, among the serpents, the 

 blind- worm or common harmless snake is the only species that appears to 

 possess an aperture of either sort ; the rest have a rudiment of the organ 

 within, but we are not acquainted with its being pervious to sound. 



Fishes are well known to possess a hearing organ, and the skate and 

 shark have the rudiment of an external ear ; but, like other fishes, thej 

 seem chiefly to receive sound by the internal tubule alone 



