M A M M A L I A. 



dous leaps which it docs when ranging its pastures, 

 but runs on all fours something after the manner of a 

 hare, so that it has always the tail ready to strike the 

 enemy when that enemy comes near. The march of 

 the kanguroo, and its organs of marching, are really 

 unique among the mammalia ; and it is impossible to 

 associate it closely with any other animal, whether 

 marsupial or not. The tail of the beaver is perhaps 

 the one that comes nearest to it in dimensions ; but 

 that is a swimming tail, or if it has any other appro- 

 priate function it consists in supporting or propping up 

 the animal, when in the act of constructing or repair- 

 ing its curious dwelling. In the length of their pos- 

 terior extremities as compared with the anterior ones, 

 and also in the length of their tails, the jerboas ap- 

 proximate the kanguroos ; but in their mode of action 

 they are altogether different; and though they too 

 are very different in their forms from the mammalia 

 with which we are more familiar, they still leave the 

 kanguroo alone in its peculiarity. 



Those which we have noticed are the most remark- 

 ble of the leaping animals ; and, with the exception 

 of hares, which, with some slight differences, are found 

 in most parts of the world, except the locality of the 

 kanguroo, they are all confined to places resembling 

 each other in their physical characters. The regions 

 which they inhabit are not exactly barren ; but they 

 consist of deserts for the greater part.with only a patch 

 of vegetation here and jthere. The leaping enables 

 the animals to clear those sandy spots which they 

 must pass, but which are too loose in their texture for 

 bearing the tread of even such comparatively small 

 animals as the jerboas. They are thus enabled to 

 subsist in pastures which could maintain no other 

 animals ; and in the case of the kanguroo, which is 

 far larger than the others, there is a considerable range 

 in the way of food ; for though the principal subsist- 

 ence is vegetable, the animal can eat animal food in 

 case of necessity ; and it is by no means unprovided 

 with weapons for killing its prey, in case living prey 

 should come in its way and be necessary. In this 

 respect it has some slight resemblance to the bears, 

 which are vegetable feeders in the main, though they 

 occasionally resort to animal food. It has not indeed 

 the terrible" hug of the more powerful bears ; but still 

 it can keep a firm hold with its fore legs, and the 

 hoof on the hind foot is a far more murderous weapon 

 in wounding than the claws on the hind foot of the 

 bear, and it is used nearly in the same manner. 



Digging or Harrowing Organs. We have al- 

 ready made some allusion to the structure of foot best 

 adapted for making way under ground, in speaking 

 of the common mole ; and we resume the subject now 

 onlv for the purpose of pointing out what particular 

 habits of animals are connected with the possession 

 of feet adapted for this purpose. They belong to 

 several of the order of mammalia, as arranged accord- 

 ing to their internal organisation, by which is meant 

 more exclusively the system of nutrition than any 

 other part of the animal, or than the whole structure 

 of the animal, as indicating a disposition, or rather 

 adaptation, for the performance of certain kinds of 

 action more than others. We shall have occasion 

 briefly to advert to the principles of this method of 

 arrangement in a future section, but we may now 

 mention that the grand distinctions are founded upon 

 the nature of the food ; and as the different, kinds of 

 food are found in different localities, the adaptation 

 of the animal to the locality where its food is princi- 



157 



pally to be found, follows as a matter of course, upon 

 that general principle, that all the provisions of nature 

 are the very best, in respect both of maximum of 

 accomplishment, and minimum of exertion required 

 for that accomplishment. 



The three divisions dependent upon food are, warm- 

 blooded or vertebrated animals ; invertebrated animals, 

 generally expressed under the name insects, though 

 these form only one class of the grand division ; and 

 vegetable substances, which include almost every part 

 of vegetable bodies, from soft pulpy fruits to dry wood. 

 With the exception of a very limited number of in- 

 vertebrated animals, some of them permanently and 

 some only in certain stages of their changeable being, 

 there are no animals which live under the surface of 

 the ground ; and therefore we may be prepared to 

 expect that the insectivorous mammalia, who have 

 their habitual dwellings, and find the whole of their 

 food there, must be but few in number. There are, 

 however, many insects, especially in countries of 

 ardent climate and great fertility, which make their 

 dwellings under ground, or construct them immedi- 

 ately upon the surface, though they find their food 

 above the surface. It is not our present province to 

 enter into the details of those animals ; but we may 

 mention that the majority of them, though not the 

 whole, are consumers of decaying vegetable matter, 

 and perform the same office in nature as animals, that 

 the fungi do as vegetables. Those creatures exist in 

 numbers beyond all arithmetic, and even all imagina- 

 tion, and in most situations where they are found the 

 use of them is seasonal. There must therefore be, 

 according to the general law of nature, which is that 

 the waste of every species tends to the destruction of 

 that species, if not removed by being applied to some 

 new purpose of usefulness, a corresponding provision 

 of animals to prey upon and regulate the myriads of 

 those creatures. For this purpose, ground animals 

 are required ; and both their protection from enemies 

 and from the heat of the day, and their means of 

 arriving readily at their food, require that they should 

 be burrowing animals, or possessed of feet adapted 

 for digging into the ground. During the day the 

 prey of those animals is, generally speaking, scattered 

 abroad ; and this renders it necessary that the ani- 

 mals themselves should be night preyers. In the 

 countries where those animals abound the most, the 

 difference of temperature between the night and the 

 day is greater than in more temperate climates, and 

 day and night are much more nearly upon an equality 

 throughout the year. Exposure to great differences 

 of temperature is one of the severest trials to which 

 the animal system can be subjected ; and as the ani- 

 mals of which we are speaking do not require to feed 

 or make any other exertion during the heat of the 

 day, it would be subjecting them to useless waste of 

 the system, and thus contrary to that wisdom which 

 pervades all nature.to have them exposed to the ardent 

 heat of the sun. To avoid this they are almost with- 

 out exception adapted for digging burrows, in which 

 they may pass their time during the heat, though of 

 course the natural instinct which leads them to dig 

 the burrow, leads them also to avail themselves of any 

 natural hole or crevice, which will afford them that 

 shelter in which they may not feel the painful sensa- 

 tions produced by exposure to the air. For this reason, 

 we find that a foot adapted for digging is very general 

 among insectivorous mammalia, whether they belong 

 to one order or another in the systematic arrangement. 



