580 



THE POPULAE EDUCATOR 



it has control ; what is part of itself, and therefore has to be 

 nourished, cherished, and defended what is foreign, and there- 

 fore may be used or avoided, as it is wholesome or noxious. 

 Indeed, the sense seems indispensable to all animals that are 

 not plunged and fixed, through every stage of their life, in the 

 midst of a medium which is both air and food to them to all 

 animals, it might be said, if it were not tautological, whose life 

 is not purely vegetable. 



In the higher animals, and in all those whose means of defence 

 lie more in their active powers than in defensive armour, the 

 sense of touch is distributed over the surface of the skin, as in 

 man. Every such animal may be compared to an island. The 

 boundary of its body is the coast-line. Along the whole of this 

 are placed, at various intervals, places of out-look, just as our 

 own tight little island has been surrounded with Martello 

 towers. These stations are few and far between where the 

 coast is rocky, abrupt, and inaccessible, but nearer together 

 at those parts where a descent could be easily made, and 

 crowded together at the outlets of ports, creeks, and river- 

 mouths, through which an active commerce is carried on. The 

 comparison of the extremities of the tactile nerves to Martello 

 towers is the more appropriate, because these have ceased to be 

 of any use in defence, and have become stations of out-look for 

 the coast-guard. So the tactile nerves are, in themselves, no 

 protection, but rather, being delicate organs, they need protec- 

 tion; few they act as alarmists, awakening and calling up the active 

 powers to fight in defence of the common country. These two 

 functions of the skin namely, that of passiVe defence and active 

 alarm are complementary to one another : where one is very 

 efficient, the cither is less needed. In the scaled and mailed 

 fishes, and in such forms as the tortoise among reptiles, and the 

 armadillo among animals, the function of sensation is sacrificed 

 to that of defence ; but in the naked skinned animals the sense 

 of touch had need be very acute. In comparing man with the 

 lower animals of that class to which he belongs, we find that 

 his sense of touch is, perhaps, better developed than that of any 

 other animal. The lower animals have to sacrifice a certain 

 amount of their surface sensibility to the paramount necessity 

 of being shielded from the cold ; or, to put it more truthfully, 

 to the retention of their animal heat. Man has neither the 

 continuous thick coating of hair of the ox, the thick skin of the 

 rhinoceros, nor the dense accumulation of fat below it which is 

 found in the pig and in the whale. He is only cosmopolitan 

 because his superior intellect enables him to clothe and house 

 himself. His nearest relatives among beasts, though much 

 better supplied with hair than himself, are confined to the 

 tropics. Man makes himself at home everywhere, but only by 

 becoming a " clothes philosopher." His triple investment of 

 ordinary, nether, and over clothing, prove him to be an exotic 

 species. He supplements by art the line of defence at those 

 points where nature has left him exposed. The main use of the 

 coating of hair is, no doubt, to defend the brute from the winter's 

 cold, but that which will keep in the heat will keep it out, so 

 that it may also be considered as a defence against the excessive 

 heat of the sun also. Doubtless the universal presence of hair on 

 the heads of both sexes of the human species indicates that in 

 his native home man had more to fear from sun-stroke than 

 from the cold of winter. Besides this, the hair is sometimes a 

 real defence against the rough usage of the outer world. Thus 

 the manes of the lion and the buffalo are real shields both against 

 trenchant blows and the worrying of the teeth of hostile animals. 

 Even the matted hair of the negro is said to be able to resist a 

 tolerably forcible sabre cut. The principal use, however, is, 

 doubtless, to defend from cold ; and it is remarkable how this 

 main object is arrived at without much prejudice to the function 

 of touch. 



Few solid substances are lighter than hair, even when pressed 

 close ; and few substances are worse conductors of heat so that 

 brutes retain their heat by the aid of a substance which costs 

 tkem but little in the way of carriage. Beyond this, the springy, 

 stiff, yet soft texture of hair, makes it always permeable to the 

 air ; and air, when motionless, is a bad conductor of heat, and 

 adds, absolutely, to weight. Hence on the coldest day, when 

 the thermometer stands below zero, the beast is still surrounded 

 with a layer of warm air, almost equal in temperature to its body. 

 So much to prove its efficiency for its main purpose. Now we 

 have to show how it leaves the sense of touch, if not unimpaired, 

 at least not obliterated. The reader must refer back to the 



illustration in Lesson XI. (page 353) to understand the structure 

 and relation of each hair to the skin in which it is developed and 

 fixed. The hair is essentially a tubular projection of the cuticle, 

 firmer and denser in its composition, being made up of closely- 

 pressed, elongated, spindle-shaped cells, instead of scale-like, 

 easily-detached ones. It is not, however, produced from the 

 level of the surface of the body, but from a bag or follicle, which 

 is always narrow, and more or less deep as the hair is long or 

 short. This horny tube dilates at the bottom of its bag to 

 enclose a vascular papilla, similar in every respect to those 

 papillse which lie immediately under the surface of the super- 

 ficial cuticle. The hair itself, like the rest of the cuticle, is 

 without sensation, as indeed it must be for the comfort of the 

 animal ; but the papilla has not only blood-vessels but nerves, 

 and is very sensitive, so that the hair cannot be pulled or moved 

 in any direction without affecting the sensitive part. Though a 

 furred animal cannot precisely tell the exact point at which it is 

 touched, on account of the length and flexibility of its individual 

 hairs, yet the sensation of touch is as truly conveyed to the true 

 skin, as it is when the pressed ridges of the forefinger of roan 

 cause feeling to be excited in the papillas beneath them. In one 

 respect hairs are even advantageous to the sense of touch, inas- 

 much as they reach considerably beyond the surface, and thus 

 the range of the sense is extended. This advantage is so far 

 recognised by nature that certain hairs are specially developed 

 which have no other use than that of touch. These may fairly 

 be described as tactile organs. These hairs are usually, and 

 almost exclusively, situated in the upper lip, projecting from the 

 most prominent part of the muzzle. In quadrupeds the snout 

 is of course the most salient part of the body, and is most used 

 in investigation. These whiskers, as they are called (though 

 they would be better named moustaches), are remarkable for 

 their length and stiffness, the depth to which their large bulbs 

 run into the skin, and even protrude in the internal surface, and 

 also for the large nerves that enter the papillae of the bulbs. 

 Those coming from the whiskers of a seal as they run together 

 look like the strands of small cords as they become woven into 

 a rope of tolerable thickness. The animals in which these 

 whiskers are most developed are the carnivora and the rodentia. 

 This is not improbably associated with the fact that these are 

 for the most part nocturnal animals. Moreover, many of the 

 rodentia inhabit holes in the ground, trees, etc. ; and many of 

 the smaller carnivora are always poking about in holes and 

 crannies for prey. It certainly would be an advantage to a fox 

 on a dark night to be able to gauge with his whiskers the size 

 of the aperture in a hen-roost before he tried to force his way 

 through it ; and thus it has been thought that there is a rela- 

 tion between the width of the body and the extreme extent of 

 the whiskers. 



In birds the place of hairs is supplied by feathers. The struc- 

 ture of these is very wonderful and beautiful, but a description, 

 of it would be out of place here, because they are certainly less 

 efficient tactile organs than hairs. Birds' feathers are coarser 

 than hairs ; they are less flexible ; they are inserted only on cer- 

 tain parts of the body ; and since there must be provision made 

 for moulting, they are more definitely cut off from the sensitive 

 skin below. For all these reasons they are not good organs for 

 transmitting the sense of touch, although they are formed in 

 tB'e same manner as hairs. Probably on account of this inap- 

 titude to transmit impressions, they are sometimes replaced by 

 hairs 1 in certain parts of the body ; but as a rule the whole of tho 

 bird's body is encircled with feathers, which lie overlapping one 

 another, and turned in one direction towards the tail of the bird, 

 in the same manner as tiles on a house-roof. A bird's jaws, 

 instead of being covered with soft, flexible and sensitive iips, 

 are covered with a hard, horny bill, and its legs, though often 

 devoid of feathers, have to be defended by scales or scutes, to 

 prevent the long tendons of their leg muscles being severed. 

 Under these circumstances, a bird enjoys little advantage from 

 its sense of touch. Indeed, it is only in the paddpd undor-sur- 

 face of the foot and toes, and sometimes in the beak and 

 tongue when the former is leathery, and the latter not capped 

 with horn where there can be any provision for the exposure 

 of a sensitive surface. It has sometimes been stated that the 

 heron, as he stands in shallow, muddy water, is guided by feeling 

 the eels twisting in and out, or even sucking his toes. This 

 statement seems rather suited for a fable of the biter bitten 

 than to be regarded as a scientific fact. That the sense is pro- 



