On the Sense of Feeling-. 299 



The scales of fishes are by no means equally arranged over the whole 

 body, sometimes being wanting on the head, and in other cases extending 

 to the tip of the snout. The fins are in this respect also variable. 



In fishes, the lateral line of scales presents many singularities, being 

 sometimes worked into grooves, at others rising into a ridge on either side 

 of the tail. The ventral scales are also frequently singular. In the her- 

 ring they are arranged so as to form a sort of external sternum. The 

 reason why fishes^ generally speaking, should be clad in scales, seems ob- 

 vious enough. Being cold-blooded, that is of a temperature varying with 

 that of the medium in which they live, they need not the warmth supplied 

 to land animals by hair, wool, feathers, etc. ; while their smooth and po- 

 lished surface enables them to glide through the water with rapidity, and 

 to pass at full speed, with perfect facility, among rocks and prominences, 

 by which a harder or less polished shield would be broken or torn. 



The epidermis, or exterior coating of fishes, is mucous and very slippery. 

 It is of course constantly moist, and it falls ofif in shreds, at certain seasons 

 of the year. 



There are some fishes, as the lampreys, niyxine, etc. whose integument 

 is entirely gelatinous, and who have no scales. As a general rule, it has 

 been observed that scales, properly so called, are confined to the higher or 

 osseous fishes ; and that osseous plates, or a naked skin, are the portion 

 of the cartilaginous. 



Let us now pass to those parts of fishes to which a more plentiful supply 

 of nervous energy is directed, and which, from their mechanism, are ca- 

 pable of becoming organs of touch. 



The appendages termed ' barbels,' which surround the mouths of the 

 silures, lates, gades, cyprins, etc. and the filamentous structure observed 

 upon the pectorals of some fishes, together with the radii from the head of 

 others, are all plentifully supplied with nerves ; and no doubt by their vi- 

 brations give notice to the animal, and enable him in some degree to 

 estimate the body before him. 



The barbels, according as they are placed round the mouth, the nostril, 

 or at the angles of the mouth, are termed labial, nasal, oral, etc. 



In fishes whose residence is in the sand, these barbels are well developed. 

 In the sturgeon, the supply of nerves to them is particularly copious. 



'i'he processes of the zeus ciliaris are employed to grapple and coil round 

 the stems of plants, and are therefore probably organs of touch. 



Organs similar to these have been described by M. Jacobson, as existing 

 in the sharhH and raifs, and which, though very difierent in their structure, 

 have been functionally compared with the feline whiskers. These organs, 

 it appears, are situated upon the lateral and inferior parts of the head, 

 and they consist of certain nodular cavities, placed at some distance be- 

 neath the skin, enveloped like the bulb of a hair in a fibrous capsule, and 

 containing within a number of nipple-shaped projections, from each of 



