178 PHYSIOLOGY 



by the same act. Besides, in some animals it is elongated so as to act 

 as an extremity or arm, as in the elephant ; or to dig, as in the hog : 

 but in these cases this elongation is only to be considered as a useful 

 part placed here for the convenience of the organ of smell, as this 

 extremity is generally employed in the affair of food. 



It is situated (as far as I know) near to, and above, the mouth in all 

 animals. 



In the Fish, which is the most imperfect animal that I know which 

 has this sense, the organ is distinct from all others 1 ; but in the Amphi- 

 bia 2 , Bird 3 , and Quadruped 4 , it communicates with the mouth. This 

 situation allows it to be an assistant to taste, or rather the remote 

 judge of proper food, while taste may be reckoned the immediate : for 

 the body which possesses the quality of odour, need not itself be in 

 contact with the organ, but only the parts possessing that quality raised 

 into vapour, and that vapour making the impression ; or the substance 

 becomes soluble in water, and that water coming in contact with the 

 organ, which becomes similar to taste. This happens to be the case 

 with Fish, which is no more than smelling the medium in which they 

 live, so that smell becomes much more extensive in its mode of reception 

 than what taste is. Indeed, I believe it is in the same proportion 

 more useful to those animals which have both : for many animals might 

 do very well without taste, which would do very ill without smell, 

 as the dog, fox, wolf, lion, cow, horse, &c. In such it would be 

 extremely inconvenient not to have it, for the operation of tasting is 

 considerable, requiring a movement of the body to be tasted, and also 

 to undergo a change, while smell is done at once. 



As the mode of application of the matter which makes the impression 

 in smell is more delicate than in touch, the organ is also more delicate 

 in its structure. The structure in the sensitive part appears to be 

 pretty much the same in all the animals possessing this organ : it is a 

 spongy or soft membrane and very vascular; which is known by injec- 

 tion. It does not appear to be covered by any cuticle. The acute 

 reception of smell by the mind is caused by quantity ; therefore the sur- 

 face of impression is extended or increased; and more especially in 

 those animals which are to, or can, distinguish their food by this sense 

 alone, and still more so in those which are to go in search of it by the 

 smell, such as the dog, tfcc. 



The operation of smell is performed, I believe, in the act of respira- 

 tion in all animals that breathe air ; and in all, excepting man, this 



1 [Hunt. Preps. Nos. 1527-1530.] -' [lb. Nos. 1531-1535.] 



s [lb. Nos. 1536-1540.] < [lb. Nos. 1552-1559.] 



