158 



MAMMALIA. 



Vegetables, generally speaking, grow partly in the 

 earth and partly in the air over it ; and in those 

 vegetables which have annual stems in the air but 

 roots in the earth, lasting for more than one year, the 

 part in the earth is the only existing part at some 

 seasons, and the most succulent part ; and therefore 

 the most nutritious food for animals at all seasons ; 

 unless when a particular portion of the root has 

 brought its annual stem, its flower, and its seeds to 

 maturity, and thus, having performed its grand func- 

 tion in nature's economy, is completely exhausted, 

 and its remains pass to the general store of inorganic 

 matter, without any assistance from a preying animal. 

 In warm countries especially, and in all countries 

 where the great alternation of the seasons is wet and 

 dry, there is a necessary perishing of annual surface 

 vegetation, unless in those succulent plants which, 

 from the peculiar texture of their covering, are proof 

 against the action of heat ; and even in them the 

 flowers, flowering stems, and all other parts immedi- 

 ately conducive to the annual production of seeds, are 

 subject to the same fate. In such countries the 

 drought penetrates to a far greater depth, and scorches 

 and withers with far more severity, than it does even 

 in those long continued courses of dry weather which 

 leave our pastures without a blade of grass. There- 

 fore, in such countries, the herbaceous plant must be 

 provided for in a manner corresponding to the severity 

 to which it is exposed. This is effected by a bulb or 

 tuber of some description or other, sometimes seated 

 above ground, sometimes placed under it, and some- 

 times partly the one and partly the other ; and from 

 the nature of the case, it must partake more or less of 

 the properties of the succulent plant, which endures 

 the ardours of a tropical sun upon the surface during 

 the dry season, according as it is more or less exposed. 



Here again there is an ample store provided for 

 those mammalia which feed upon succulent vege- 

 tables, and this store requires a digging foot, in order 

 that it may be arrived at with the least labour by the 

 animals which subsist upon it. But in the dry season 

 of such countries the nether air and the surface of the 

 earth react in consequence of the surface of the earth 

 sinking lower in temperature than the air over it 

 does ; and the variation not being diminished to the 

 same extent from its extending freely to the cloud- 

 less sky, this occasions a heavy fall of dew, which 

 softens the surface, as well as makes " the scent" of 

 those bulbs upon which the animal feed, " lie," as the 

 sportsmen express it. Those circumstances taken 

 together tend to render such animals nocturnal feeders; 

 and the very same reason which makes the nocturnal 

 feeders, formerly alluded to, burrowers, applies to 

 those under consideration, so that even the vegetable 

 feeders of those burnt up countries live in burrows 

 during the day, and come abroad only during the 

 night. 



Succulent vegetable matter, such as that which is 

 found in bulbs and tubers, and often in roots differently 

 formed from those, while they remain in the earth, 

 without any strong action of parts in the air, may be 

 considered'as a sort of intermediate link between the 

 flesh of animals and the leaves of fibrous parts of plants, 

 which have been elaborated under the influence of 

 the atmosphere, and especially of light. We do not 

 mean to say, that in a physiological point of view, this 

 matter is as much akin to animal matter as to vege- 

 table, for it is strictly vegetable matter ; but when 

 we consider it merely as the food of mammalia, or 



indeed of any animals, it holds the medium place 

 which we have assigned it. It is the same with the 

 farinaceous part of the seeds of vegetables, which 

 elaborated under a protection from the severe action 

 of light, and are all pulps in the inmature state, and 

 in so far reducible to pulp again by the action of heat 

 and moisture, without the immediate contact of the 

 free atmosphere, and the immediate influence of the 

 rays of the sun. This is the same whether those seeds 

 are produced on perennial trees and shrubs, or upon 

 annual stems, and the seeds are shed and scattered 

 on the ground, at the very time when the annual 

 stemmed plant, which has a root of more than one 

 year's duration, or produces new roots every season, 

 is down in the bulb, stemless, and in a state of com- 

 parative repose. Those seeds do not, under ordinary 

 circumstances, get so deep under the surface as the 

 roots do, but they fall in concealment among the 

 remains of that vegetation which has performed its 

 functions during the season, and is passing into decay. 

 Those seeds are in fertile places so exceedingly nu- 

 merous, that if a very large portion of them were not 

 removed, they would have no room to vegetate, but 

 would perish by whole races every year. The pre- 

 vention of this requires a great number of small 

 ground animals, of which the rat family may be con- 

 sidered as the chief; and the vast numbers in which 

 these animals occur in almost every country under 

 the canopy of heaven, is a proof of their high im- 

 portance in the economy of nature. The jerboas 

 already alluded to are members of this great family, 

 and though they are the most characteristic leapers, 

 and the most decidedly formed for the purpose of 

 leaping, the hind legs of all are more or less provided 

 with canon bones, and the fore legs have more or 

 less of cross motion, and the toes well developed and 

 free, so that they can answer partially as hands, both 

 for conveying the food to the mouth and for grasping 

 while the animal stands erect on the hind legs, 

 or holding the food, until it is divided by the action 

 of the incisive teeth, which are remarkably free, well- 

 formed, and powerful in all such animals. 



The food of this family, and the places in which 

 they have to seek for it, point to a nocturnal habit, 

 and the possession of digging feet, as well as those of 

 the feeders upon ground insects and the roots of 

 plants ; and observation shows that the manners of 

 the animals are in perfect accordance with this. 

 During the heat of the day, or in the clear light, 

 "there is not a mouse stirring;" and in towns rats 

 take up their habitations by thousands in the common 

 sewers and drainages. It is the same with the whole 

 family ; for they inhabit in darkness during the day 

 even where they come freely abroad during the night. 

 They are all furnished with eyes of remarkable bright- 

 ness ; and from this we may conclude that they see 

 objects by far dimmer light than any animal can do, 

 though there is no reason to suppose that even they 

 can distinguish objects by vision in the very darkness 

 of night. It is highly probable that scent is their 

 most powerful sense ; for we find that traps set for 

 the capture of rats and mice must be baited with odo- 

 riferous substances ; but it is also probable that their 

 hearing is also acute. They do not require this for 

 conducting their own labours in the finding of 

 their food, so much as they require the sense of 

 smelling, because their chief food does not stir or 

 make a noise so that they could be guided to it by 

 the ear. 



