298 On the Sense of Feeling. 



sensitive. The wliole lower surface of such animals admits of being minutely 

 injected, exliibiting the increased vascularity which is said to accompany 

 sensation. 



The first class of raollusca, the cephalopodes, are in many respects very 

 singular animals. In them is found the first rudiment of an ear, and their 

 teutacula are numerous and flexible. In the cuttle fish, under favourable 

 circumstances, they enclose a circle of twenty or thirty feet diameter, and 

 have been known to close upon and drown native divers, wlio had de- 

 scended to obtain the animal as an article of food. 



Fishes, to ascend to the vertebrated animals, are by no means remark- 

 able for the delicacy of their tact ; for being without extremities, and con- 

 sequently being incapable of grasping any object save with their mouth) 

 such a sense extended over their body would be useless and perhaps pre- 

 judicial to them. Upon the lips and snout, their natural organs of pre- 

 hension, we do, not unfrequently, find this sense to be bestowed. 



The integument of the greater number of fishes is familiar to all under 

 the appellation of scales ^ these being horny, and in some cases calcareous 

 laminae, overlapping one another, and forming, with the metallic hues of 

 their pigment, a complete and brilliant covering. 



Scales are developed upon the surface of the cutis, from which they are 

 not distinctly separable. The manner of their production is obscure, since 

 they have no bulbs like hair or feathers. They are, I believe, at present 

 supposed to be secreted by the vascular membrane j rising in a sort of 

 flattened pouch of that membrane, composed of a series of flattened cones, 

 and shooting out in a radiated direction according to the figure of the indi- 

 vidual scales. The scales of the greater number of fishes are arranged in 

 an 'imbricated' manner, that is to say, like the tiles of a roof, each scale 

 being marked by striae parallel to its sides, or proceeding in a radiated 

 manner to its plane or indented margin. 



In some fishes, as the bichir, etc. the scales are very thick, but only 

 slightly overlapping , although, being strong, serrated, and set very close, 

 they form a very secure covering. 



In certain other fishes, as the eel, the scales do not overlap at all, but 

 fit neatly together, and are encrusted by a strong epidermis. Analogous 

 in some respects to this is the integument of certain mammalia of the seal 

 family, familiar in a dried state to us all. There the cutis is strong and 

 fibrous, and presents a series of rough prominences of greater or less size, 

 in various parts of the body, forming when dry the seal skin of commerce. 



In the diodons and tetraodons, this structure is still further developed, 

 forming sharp prickles or spines, manageable by a general muscle con- 

 nected with their bases. 



In the cyclopterus, or lump fish, the scales are conoidal or tubercular, 

 varying in size, and adhering by their base to the integument, but leaving 

 an unprotected vacuity between each. 



