M A M M A L I A. 



Kit 



also bear, generally speaking, a less proportion to 

 the quantity of flesh ; and the flesh, including all the 

 membranous and cellular tissues, as well as the mus- 

 cular or fibrous parts, is much more hard and compact. 

 The flesh, for instance, of an old ox, or an old sheep, 

 which has been left nearly to nature in a suitable 

 pasture, is tender and juicy, while that of an old lion 

 is as tough as cables. 



There are great gradations in this respect ; and 

 perhaps the instances which we have taken form 

 nearly the extreme limits among the more character- 

 istic mammalia ; but we invariably find that as the 

 animal approximates the typical one, which moves 

 vigorously but briefly, there is a spareness and con- 

 densation in all the soft parts; and that in proportion 

 as it approximates the opposite type, the soft parts 

 become the more relaxed. 



We find this exemplified in almost every species 

 of domesticated animal, and man himself does not 

 form an exception. There is no instance in which 

 this is more remarkable than in the horse an animal 

 which is so obedient to breeding and training, that 

 horses may be reared for almost any specific purpose 

 to which such an animal can be applied, from the 

 utmost speed of the racehorse, the more continued 

 but less rapid motion of the hunter, to those unwieldy 

 horses which appear to feel the burden of their own 

 weight. It is not meant to be said that the whole 

 character of the animal can be entirely changed' to 

 any single purpose, and thereby unfitted for every 

 other, for no training can acquire so perfect a com- 

 marid as this over an animal ; but still it is true that 

 proper skill in the selection of the breed and in the 

 training, can make the animal better adapted for some 

 one particular purpose than for any other, arid far 

 better adapted for it than any other animal not 

 trained in this particular manner. It is indeed this 

 susceptibility of training, and consequent adaptation 

 to a great number of purposes, which renders the 

 horse so superior to all others as a working animal. 

 The ass is stronger, more hardy, and more healthy ; 

 and the camel and the bullock can undergo fatigue 

 under a load which no horse could endure ; but when 

 it has been said of these animals that they are efficient 

 beasts of burden the tale of their whole history is told. 



There are some of the elements wanting in order 

 to perceive physiologically how those general changes 

 in the animal system are brought about ; and the 

 chief one is our ignorance of the origin of animal 

 motion. As we shall afterwards see, we can reduce 

 it to a very simple fact, namely, that of the shortening 

 and the thickening of a fibre; but though there have 

 been many hypotheses upon the subject, we never 

 can say why, or by what means, this shortening of the 

 fibre takes place. We are certain, however, that it 

 exhausts the animal in proportion to the rapidity 

 with which it takes place, or in proportion to the 

 quantity in a given time ; but we have no means of 

 estimating the strength of the original impulse in 

 which this effort originates, because the impulse is 

 not matter, and therefore we can only see its effect in 

 the change which it produces on matter. 



It is highly probable that this is a point upon 

 which we shall never obtain any knowledge, and that 

 we must content ourselves with the simple fact which 

 we can observe ; and this, though it is a little humbling 

 to our pride, is of some advantage in pointing out the 

 limits beyond which, if we attempt to use words, 

 those words can have no meaning. 



It is not necessary to point out particularly the 

 more conspicuous external parts of the mammalia, for 

 every one is familiar with them in some species, and, 

 as we have said, there is a common type, or general 

 resemblance that runs through the whole, but which 

 admits of very considerable variety in all the indi- 

 vidual parts. A head, a trunk, or body as it is usuallv 

 called, and four extremities or limbs, are the chief 

 parts; though in some species, especially those mam- 

 malia which swim, the posterior legs are united with 

 the tail, forming a sort of fin ; but this fin, even where 

 most perfect, is never like the fin of a fish, any more 

 than the membranes of bats and other flying mammalia 

 resemble the wings of birds. When we consider 

 those swimming and flying appendages of an animal 

 of this class, we always consider them as departures 

 from that which we take as the proper typical form 

 of mammalia ; and that, for example, though a whale 

 lives in the sea, and is a most efficient swimmer in 

 that element, yet that it is not the model of a sea 

 animal, but a land one adapted to an aquatic habit. So 

 also, though we find the bats in many instances inca- 

 pable of motion upon the ground, while they fly readily, 

 though heavily and in a flutter, yet we do not con- 

 sider them as the characteristic inhabitants of the 

 atmosphere, which range there with freedom, and 

 buoyant and elegant flight. The owls have too many 

 soft feathers in proportion to their weight for being 

 graceful fliers ; but still if a bat and owl are seen 

 on flight at the same time, the flight of the owl is 

 beyond all comparison more graceful than that of 

 the bat, and the animal appears to be far more in its 

 element. 



We do not mean to say that it actually is so ; for 

 the whale in the sea, and the bat in the gloomy cave, 

 are just as much at home and as beautifully adapted 

 to their situations, as the wild deer on the mountain 

 or the eagle in mid-air. We must, however, take 

 some distinctions which are more general than those 

 of single species, before we can get anything like a 

 an index to the facts of natural historj', or to serve as 

 an artificial memory to bring them to our recollection 

 when they are necessary; and therefore we must take 

 some one species, consider it as typical, and distin- 

 guish the rest according as they vary from this type. 



This is a part of the subject upon which a good 

 deal of caution is necessary, because the selecting of 

 a particular type is our work, and not the work of 

 nature ; and whenever we mix our own work with 

 nature's work, we always stand in jeopardy of laying 

 too much stress upon our own, and giving it an 

 importance to which it has no claim. We ought 

 distinctly to bear in mind that our systems of arrange- 

 ment are not knowledge, any more than words are 

 thoughts; but the system and the words are alike 

 necessary for the purposes of communicating ; and 

 it is our fault if we lose the substance in our vain 

 attempts to catch the shadow. 



It is not so necessary to mention this precaution in 

 the case of animals generally, and in that of the mam- 

 malia in particular, as it is in the vegetable world ; 

 for the vegetable, rooted in the soil, must summer 

 and winter in the same spot ; and as whatever must 

 naturally abide the blast is always tempered by 

 nature to the blast, the vegetable is far more under 

 the controul of external circumstances, and therefore 

 subject to far greater variations of structure, than 

 any animal, and more especially than the mammalia, 

 which have much more acute sensation to warn thera 



