2S8 ADDITIONAL NOTES. 



torpedo, on the contrary, is instantly killed by removal from salt 

 to fresh, water, even more rapidly than if left exposed to the 

 atmosphere. Such differences, so strongly marked, are deserving 

 of the attention of the physiologist. — J. D. 



{On the Senses of Fishes, page 26.) 



That fishes have the sense of smell, may be inferred from 

 the structure of their nostrils, as well as front the fact 

 mentioned in note, page 26. Munro, in his work on "The 

 Structure and Physiology of Fishes," published in 1785, rea- 

 soning from the ample and peculiar manner in which these 

 parts are supplied with olfactory nerves, came to the conclu- 

 sion "that they (fishes) are much more sensible of odorous 

 bodies dissolved in water, and applied by its medium, than 

 we should be, if the application of the object was to be 

 made to an organ of smell through the same medium." The 

 statement of the author, in page 26, founded, probably, on 

 analogy, " that the principal use of the nostrils in fishes is to 

 assist the propulsion of water through the gills, for performing 

 the office of respiration," is not borne out by the structure of 

 the parts. Each nostril has commonly two external apertures. 

 They are well marked in the Salmonidae — one free, the anterior, 

 for the admission of water to the plicated membrane on which 

 the nerve of smell is distributed ; the other, the posterior, 

 often valvular, by which the water passes out. The absence, 

 indeed, of such an opening of communication between the nos- 

 trils and pharynx, is one of the characteristics by which fishes 

 and reptiles in their greatest generality are distinguished. 



Whether fishes have the sense of taste, has been held to be 

 doubtful, as papillae, it is said, have not yet been detected in 

 their tongues. But in considering the question, it should be 

 kept in mind that this sense has been enjoyed without papillae, 

 without a tongue (see the well-authenticated case recorded in 

 the Phil. Trans. 1742 and 1747), and that it is probable it is 

 more or less perceived whenever there are branches of the gus- 



if put into an equal quantity of fresh water ; whilst another immersed in a 

 solution of higher sp. gr., viz. 1048, which is much salter than sea water, died 

 in a few minutes, as did also a young parr similarly treated.— J. D.] 



