

may bo staU'il that tho groat actr 





.an on tho cironmscribod 

 senso of t < 

 Tin cold-blooded aiii: :io8 and finli) difTVr from the 



warm-blood. .! (nialnm.. .' for tho i- 



i8 no non-conducting or heat-rrt 



Hairs and feathers are admirable retainers of heat ; but scales 

 and Bcutos, though good to roust blown and pressure, allow beat 

 to pass out or in v. ,,-h rosistanoo. This, of course, U 



MMMiaUd with tho fact tlia avo but littlo 



It duiM n.it follow, however, that because tho 



iroly dofoudod by scales, wh. 



i> tlio insertions of those next behind them in a 

 iimiiin-r \\liirii 1, i-.illrd imbricated," that therefore they are 

 riitirrly wit!. mo of touch. Tho scales are developed 



iiiuc-h m the human nail- aiv, and we know that these are them- 

 ui-cn<ilil ; yd they are BO intimately connected with 

 tho sensitive parta by which they are formed, that tho nails are 

 the COL acute, and even morbid sensation. Tho quick 



i'f tlir nail is proverbially sensitive to pain; witness tho common 

 phrase of being wounded, or cut to tho quick. Reptiles, how- 

 ever, slough at certain seasons, and the old skin, dissevered 

 from tho cutis, adheres to them for somo time in fact, until a 

 new and complete armour is formed below. During such periods, 

 and inforentially at all times, the senso of touch cannot bo 

 acntc. Scaled reptiles may be olive to blows or pressure, but 

 hardly to those sensations of soft touch which convey tho most 

 distinct impressions of all to ns. These remarks apply with yet 

 more force to the hard, stony, surface of tho bocks of crocodiles. 

 The under side of the body of crocodiles is leathery rather than 

 stony, and has fewer stony masses on its surface, and this is 

 therefore sensitive. Sir Emerson Tennent gives an amusing 

 account of a cayman, which he surprised before it could make 

 its retreat. Tho Ceylon crocodile threw itself on its side, and 

 feigned death ; but when it was tickled under its arm it found 

 the process too much for its gravity, and finally got up and 

 hobbled away. As wo before remarked in the article on taste, 

 the tongue is made use of by serpents and lizards to touch 

 objects with ; and this is probably its main, if not its only use. 

 In conformity with tho assertion that nocturnal animals often 

 have specially modified organs of touch, wo find that certain 

 nocturnal tree-snakes have their snouts prolonged into tactile 

 organs. 



The large majority of fish are completely closed in by plates 

 tmd scales. With few exceptions even the lips are hard and 

 dry, so that they need to have some special organs of touch. 

 Sometimes certain rays of tho fins are detached from the oar- 

 liko parts, and become long styliform organs of touch. When 

 this is the case, they arc clothed with soft parts, which aro well 

 supplied with nerves. Thus, in tho gurnet throe soft rays aro 

 told off from the front of tlio pectoral fin, to form feeling 

 fingers. It is curious that in a creature so for removed from 

 man wo hare the samo parts modified to tho samo use, though 

 in almost all tho intermediate animals this part has a different 

 function. In the angler two rays detached from tho bock fin, 

 and situated on tho top of tho head, have this function, but tho 

 nso to which ho puts these feelers is remarkable. One of tho 

 feelers has at its end a flattened, shining, and flexible adjunct, 

 and this is used as a bait, just as a silver strip is used by tho 

 iroller. Tho angler is rapacious, but sluggish ; ho therefore 

 lies on the bottom, with his huge, ugly mouth wido open, and 

 stirs up the mud with his fins to conceal himself, while ho 

 drops his sensitive bait before his mouth and keeps twitching it 

 about, until he feels some hapless fish begin to nibble, when he 

 makes a forward rush and closes his mouth upon him. The 

 "whole of each of tho four limbs of tho lepi Jo-siren are converted 

 into organs of touch. For tho most part, however, tho limbs of 

 fish which correspond to our legs and arms are entirely devoted 

 to locomotion, while quite new structures are developed for them 

 to feel with. These special tactile organs are called barbules. 

 They aro placed on tho head, and generally at tho fore part of 

 the jaws. When on or under the lower jaw they may be single ; 

 but they are more often, and when on tho upper jaw always, in 

 pairs. Two instances are given in the illustration : tho one 

 shows how they occur in an ecl-liko fish, and tho other in an 

 ordinary-limbed fish. Tho single medial barbulo under tho jaw 

 of tho cod is a familiar example. It is supposed that a cod 



. .ut blind when caught had obtained its food to well by 

 1 it was quitu in good condition. IlarbuJw are 

 well adapted to tho purpose of touch. If in any other way 

 nerrM were conveyed through the scaly covering and Mpoeoil. 

 these delicate structures would be liable to bo injured by the 

 impact of hard external bodies, which would be crushed between 

 them and the hard and underlying MalM ; bat noee the main 

 nerve of the*e barbate* accompanies a cartilaginous core, and 

 since it Bpring* from a single point to be spread upon a flexible 

 pillar which hard bodies would drive before them, the chance of 

 having the nerve crushed is much roduocd. Barbaloa are for 

 the most part found on the jaws of grovelling fishes like stur- 

 geon* and barbels, which foel along the bottom for all kinds of 

 garbage which may have sank there. 



The mollusca have received their name from their general 

 character of softness ; moUit being the Latin adjective for soft. 

 This namo was given them by Cavier to contrast them with the 

 hard-coated insects and Crustacea which belong to the sub- 

 kingdom artioulata. Hence in those species which are not pro- 

 \ i.l-i with a shell, and in the exposed parts of those spunies 

 which have this protection, there is a soft, sensitive !"'" The 

 skin, however, in this sub-kingdom has often superadded to the 

 functions which it possesses in vertebrata the inw&om of respi- 

 ration and of locomotion. Even those parts where the sense M 

 more or less localised have so many other offices to which the 

 sense is secondary or subservient, that it would lead us too far 

 from our subject to describe them. It U true that the gastero- 

 poda have horns as special tactile organs ; but we find in thft 

 cephalopoda tho sense of touch is intimately combined in th^t 

 arms with the elaborate apparatus for grasping and holding t^Mitr 

 prey ; and in tho brachiopods the sense is united with the organ* 

 for breathing and keeping up currents in the water. We moat, 

 therefore, avoid going into details in reference to them. It may 

 be stated generally, that the slower an .nim^l moves, and the 

 more fixed its station, the more will its sense of touch be deve- 

 loped in proportion to the other senses. Hence the sense of 

 touch is well developed throughout this sub-kingdom. Soft 

 bodies aro ill-suited to energetic motion ; but soft bodies are 

 well adapted to receive tactile impressions. In those ""tn^l 

 of this sub-kingdom which are wholly fixed, the organs of touch 

 are multiplied ; and in tho lowest class of all there is a hmso 

 shoe-shaped or circular series of tentacles round the mouth, 

 which aro extremely sensitive. This arrangement of feelers 

 around the mouth is so general a character of fixed *n;>n*l 

 that there is a striking similarity between the outward form of 

 these lower molluscs and the fixed animals of the sub-kingdom 

 coclenterata, although tho essential organs are quite different. 



The articulata (though some of them are soft-skinned) are for 

 the most part covered with a hard, horny covering, which is as 

 resisting as plate-armour. It is therefore necessary that these 

 animals should have special organs of touch. We have already 

 referred to those of the lobster and its tribe in a former number. 

 Insects have, developed from their heads and mouth-organs, 

 jointed rods, which have nerves of touch running to them and 

 up into them. These jointed rods are covered with hard, horny 

 matter, like the rest of tho body ; but sometimes the last joint 

 exposes a naked membrane, and where this is not the case, the 

 jointed and therefore flexible nature of the organs make them 

 capable of receiving impressions of touch, and of measuring the 

 dimensions and resistance offered by external objects. The 

 normal number and position of these organs will be seen in the 

 illustration. There aro two long, many-jointed ones jutting from 

 tho head ; these ore colled tho antenna;. Another pair (or pairs) 

 spring from tho lower lateral jaws ; they aro called tho maxillary 

 palpi. Another pair (or pairs) spring from the rides of the 

 lower lip ; these aro called the labi palpi. The soft-skinned 

 spiders have no antenna) or labi palpi, but their maxillary palpi 

 aro so long and large as to look like legs. 



Tho cchinoderms, or sea-urchins, are so enclosed in their more 

 or less spherical boxes of hard shell, that a casual observer would 

 suppose them to bo unfeeling wretches, capable of inflicting 

 wounds with their long spines, but insensible to softer emo- 

 tions. This is not tho case, however, for they can protrude 

 through tho small holes which perforate the shell and occupy five 

 doublo meridional bands of their globular boxes, a multitude of 

 soft, tubular, sucking feet, to each of which there runs a nerve. 

 Tho sea-anemone, with its streaming foolers, lives by feel- 

 ing; and the whole sub-kingdom to which it belongs u 



