348 FISHES. 



which receives many nerves from the eighth pair, and which, as it 

 seems nearly to correspond to the pharyngean teeth, so powerful in 

 animals, appears to have all the dispositions calculated to make them 

 relish the food ; but it would be very difficult indeed to determine the 

 reality of this conjecture. 



This organ is very remarkable for a peculiar kind of irritability ; if 

 we touch or prick it, the point pricked swells up, and assumes for a 

 few moments, the form of a cone ; this irritation may be repeated on 

 every point of the organ, and always with the same effect as long as 

 life remains in it, and Ave know that life subsists a long time in the 

 carp, even after the head has been cut off. 



This phenomenon might be made the object of interesting physio- 

 logical experiments. 



Organs of Touch. 



Fishes are not much more highly favoured in regard of touch, 

 than they are with respect to the organ of taste ; being destitute of 

 prolonged members, and particularly of flexible fingers, calculated to 

 grasp objects, it is only by their lips, that they can ascertain the forms 

 of bodies : the appendices called cirri, such as many of them, as the 

 silures, several cods and cyprins, have round the mouth; the filaments 

 or rays detached from the pectoral fin, which have been called fingers 

 in the mullets and polynemes ; the other moveable rays, with which 

 the head of baudroies is provided, and which are detached from the 

 first dorsal fin, serve rather to enable them to perceive the approach 

 of foreign bodies, than to rocognize their forms and other tangible 

 qualities ; however in the limits to which they are restricted, these 

 organs possess great sensibility, and receive nerves of considerable 

 size. 



The general covering of the body of fishes, at least in those in 

 which that part is covered with scales, cannot have any high degree 

 of sensibility ; but in this respect the varieties are almost infinite, from 

 the species, which like the lamprey seem to have nothing resembling 

 scales, or those which like the eel, have them small and thin, and as it 

 were, lost in a thick epidermis, to those in which the scales form 

 osseous bucklers, as in the sturgeon, or constitute by their union an 

 inflexible cuirass, as in the coffres. 



The scales are productions of the same nature as the nails or horns, 

 but most commonly of a more calcarious substance, with which the 

 skin of fishes is furnished. 



The chemical composition of scales, has a great analogy with that 

 of the bones and teeth. M. Chevreul analyzed the scales of a lepisos- 

 teus, a chcetodon, and a bar, and obtained the following results, after 

 having evaporated the water by exposing them for six weeks, in a dry 



vafimm* 



* By drying, the lepisostic had lost 11,75 per cent., the chcetodon 13, the 

 bar 16. 



