26 SALMON I A. [SECOND DAY. 



it is but a rude imitation of nature ; and from the 

 greedy manner in which it is seized, fish, I think, 

 cannot possess a refined sense of smell, or any nervous 

 system corresponding to the nasal one in animals that 

 breathe air : no scent can be given to water by an 

 artificial fly, or, at least, none like that of the natural fly. 

 HAL. The principal use of the nostrils in fishes, T 

 believe, is to assist in the propulsion of water through 

 the gills for performing the office of respiration ; but I 

 think there are some nerves in these organs which 

 give fishes a sense of the qualities of the water, or of 

 substances dissolved in, or diffused through it, similar 

 to our sense of smell, or, perhaps, rather our sense of 

 taste, for there can be no doubt that fishes are attracted 

 by scented pastes and scented worms, which are some- 

 times used by anglers who employ ground-baits ; and 

 in old angling-books there are usually receipts for 

 attracting fish in this manner, and though the absurdity 

 of many of these prescriptions is manifest, yet I do 

 not think this proves that they are entirely useless, 

 for, upon such principles, all the remedies for diseases 

 in the old pharmacopoeias would be null.* 



* [That the olfactory nerves in fishes are destined for the same 

 function as these nerves in the mammalia, seems hardly to admit of 

 doubt, especially considering the fact, that we can perceive odours 

 when the head is immersed in water : this is easily proved by plunging 

 the head in water to which some eau-de-Cologne or other scent has 

 been added ; on drawing in the water through the nostrils, the peculiar 

 odour (as I have ascertained) is distinctly perceived. J. D.] 



